Physical Pharmacy Notes 39101b
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§ §
Physical Pharmacy •
application of physical chemistry in pharmacy
•
study of physiochemical properties of substances used in drug formulation
FORCES OF ATTRACTION Intramolecular Forces •
forces of attraction within the molecule
•
Types – Ionic & Covalent Bonds o Ionic Bond § Transfer of electrons between a non metal & a metal § observed in formation of salts o Covalent Bond § sharing of electrons between two non metals § observed in organic compounds
Intramolecular Forces •
forces of attraction between molecules
•
Types – Binding & Attractive Forces o Binding Forces § Cohesion – similar molecules § Adhesion – different molecules § Repulsive – prevent molecules from annihilating each other o Attractive Forces § Van der Waals § Hydrogen Bond § Ion-Dipole § Ion-induced Dipole
Van der Waals Forces •
weak forces that involve the dispersion of charge across a molecule called a dipole o Keesom Forces (orientation effect) § Dipole-dipole § molecules are polar with permanent polar dipoles § Ex. water, HCl, ethanol, acetone, phenol o Debye Forces (induction effect) § Dipole-induced dipole § transient dipole induced by a permanent dipole § polar molecules produces temporary electric dipole in nonpolar molecules § Ex. Ethyl acetate, methylene chloride, ether o London Forces (dispersion effect) § Induced dipole- induced dipole § induce polarity between non polar molecules
responsible for liquefaction of gases Ex. Carbon disulfide, CCl2, hexane
Hydrogen Bond •
electrostatic interaction of H with highly electronegative atoms (S,N,Cl,F,O)
•
s for unusual properties of water
Ion-Dipole Interaction •
polar molecules are attracted to either positive or negative charges
•
occurs when salt is dissolved in a polar solvent
•
solubility if crystalline substances in H2O
•
quaternary ammonium + tertiary amine
Ion-Induced Dipole •
induced by close proximity of a charged ion to a non polar molecule
•
responsible for the solubility of non polar molecules
•
Ex. Iodine complex with salts
PHYSICAL PROPERTIES OF MATTER Additive •
depends on the total contribution of the atoms in the molecules
•
Ex. MW, Mass
•
↑ atoms = ↑MW = ↑Mass
Constitutive •
depends on the arrangement of the number & kind of atoms within a molecule
•
Ex. Refactive Index, Optical Rotation
Colligative •
function of the number of species or particles present in a given solution
•
Ex. Osmotic pressure elevation, Vapor Pressure lowering, Freezing Point Depression, Boiling Point Elevation
TYPES OF PROPERTIES Intensive •
independent of the amount of the substance in the system
•
Ex. Temperature, Pressure, Density, Viscosity, Surface tension, Specific Gravity
Extensive •
depends on the quantity of substance in the system
•
Ex. Mass, Length, Volume
Lorenzo Dominick Cid 2015
P1 & P2 = vapor pressures at T1 & T2 ∆Hv = molar heat of vaporization R = 1.987 cal/mole deg
STATES OF MATTER The Gaseous State Gas Laws •
refers to an ideal situation where no intermolecular interactions exist and collisions are perfectly elastic
•
there is no energy exchanged upon collision
•
Boyle’s Law o relates volume and pressure o constant temperature o PV = k
•
•
Gay-Lussac and Charles’ Law o states that the volume and absolute temperature of a gas at constant pressure are directly proportional o V = kT Ideal Gas Law o PV = nRT o R = 0.08205 liter.atm/mole.K or 8.314 joules/mole.K or 1.987 cal/mole deg o n = number of moles
The Solid State •
have fixed shapes
•
nearly incompressible
•
have strong intermolecular forces
•
very little kinetic energy
•
atoms vibrate fixed positions about an equilibrium position, & so there is very little transitional motion
Crystalline Solids •
Solids whose structural units are arranged in a fixed geometric pattern or lattices
•
definite shape
•
orderly arrangement of units
•
definite and sharp melting points
•
6 Distinct Critical Systems Based on Symmetry o Cubic – Sodium Chloride o Tetragonal – Urea o Hexagonal – Iodoform o Monoclinic – Sucrose o Rhombic – I2 o Triclinic – Boric Acid
Kinetic Molecular Theory •
Gases are composed of particles called atoms or molecules, the total volume of which is so small as to be negligible in relation to the volume of the space in which the molecules are confined
•
The particles of the gas do not attract one another, but instead move with complete independence
•
The particles exhibit continuous random motion owing to their kinetic energy
•
glasses or supercooled liquids
•
molecules are arranged in a random manner
The molecules exhibit perfect elasticity
•
no definite melting points
•
faster dissolution rate
•
The Liquid State • •
• •
Critical temperature – temperature above which a liquid can no longer exist Critical Pressure o pressure required to liquefy a gas a critical temperature o highest vapor pressure of a liquid
Polymorphism •
condition where substances can exist in more than 1 crystalline form
•
polymorphs have different melting points, x-ray crystals and diffraction patterns and solubility
•
Theobroma Oil Polymorphs (Melting Points)
Boiling Point – the temp at which the vapor pressure of the liquid equals the external and atmospheric pressure
o
Unstable γ form à 18°C
o
α form à 22°C
Latent Heat of Vaporization o the quantity of heat taken up when a liquid vaporizes o it is liberated when a vapor condenses with a liquid
o
β prime form à 28°C
o
Stable β form à 34°C
Clausius-Clapeyron Equation •
Amorphous Solids
relationship of vapor pressure and absolute temperature of a liquid
log
•
Types of Polymorphism o Enantiotropic – reversible o Monotropic – unidirectional transition
Freezing Point •
temperature at which liquid à solid
•
melting point of a pure crystalline compound
P1 ∆Hv (T2 -T1 ) = P2 2.303 RT1 T2
Lorenzo Dominick Cid 2015
Latent Heat of Fusion •
Energy absorbed when 1g of a solid melts
•
Heat liberated when it freezes
Liquid Crystalline State •
liquid crystals à intermediate between liquid and solid states
•
may result from the heating of solids (thermotropic) or from the action of certain solvents on solids (lyotropic liquid crystals)
Two Main Types of Liquid Crystals •
•
Smectic o Soaplike or greaselike o molecules are mobile in 2 directions o rotates in 1 axis Nematic o o o o
threadlike molecules are mobile in 3 directions rotates in 1 axis Cholesteric – special type of nematic
Supercritical Fluids
THERMODYNAMICS •
deals with the quantitative relationships of interconversion of the various forms of energy
•
System – a well defined part of the universe under study
•
Surroundings – the rest of the universe from which the observations are made
•
Boundaries – physical or virtual barriers that separate a system from the surroundings
Types of Systems •
Open – energy and matter can be exchanged with the surroundings
•
Closed – energy can be exchange with the surroundings but not matter
•
Isolated – neither matter not energy can be exchanged with the surroundings
First Law of Thermodynamics •
Energy cannot be created nor destroyed, it can only be transformed into a different form
•
Adiabatic – constant heat
•
Isothermic – constant temperature Isochoric – constant volume Isobaric – constant pressure
•
properties intermediate between those of liquids and gases
•
•
formed from the gaseous state where the gas is held under a combination of temperatures and pressures that exceed the critical point of a substance
•
Second Law of Thermodynamics •
Refers to the probability of the occurrence of a process based on the tendency of a system to approach a state of energy equilibrium
•
Entropy
THE PHASE RULE (GIBB’S PHASE RULE) •
relates the effect of the least number of independent variables (T, P & C) among the various phases (S,L & G) that can exist in an equilibrium system containing a given number of components
Third Law of Thermodynamics •
𝐹 =𝐶−𝑃+𝑋 F = no. of degrees of freedom C = no. chemical components P = no. of phases X = variable dependent upod considerations of the phase diagram •
F – least number of intensive/independent variables that must be fixed to describe the system completely
•
C – smallest number of constituents by which the composition of each pase in the system at equilibrium can be expressed in the form of a chemical formula or equation
•
P – number of homogenous physically distinct portion of a system that is seperated from other portions of the system by bounding surfaces
•
1 Phase – F=2 – Bivariant
•
2 Phases – F=1 – Univariant
•
3 Phases – F=0 – Invariant
The entropy of a pure crystalline substance is zero at absolute zero because the crystal arrangement must show the greatest orderliness at this temperature
CONDENSED SYSTEMS •
S & L phases only
•
the vapor state is disregarded with an assumption of working at a pressure at 1atm o 2 Components – liquid phases o 2 Components – S & L – eutectic mixtures o 3 Components
Two Component System Containing Two Liquids •
Binodal Curve – area within the curve which represent a 2 phase system
•
Upper Consolute/Critical Solution Temperature – max. temperature at which two phase region in the phase diagram of a two-component system containing two liquids will exist
Lorenzo Dominick Cid 2015
•
Tie line o o
•
Sedimentation line from which a system seperates into phases of constant composition approximates proportion of components in a particular temperature
Conjugate Phases o phases of constant composition that separate when a mixture is prepared within the boundary of the 2phase system
Two Component System Containing Solid and Liquid •
Eutectic Point o minimum temp. where both exist in liquid form o point where solid A, solid B & the liquid phase coexist
Three Component System
•
Andreasen apparatus
•
↑ Sedimentation rate = ↑ Particle size (direct proportionality)
•
follow the Stoke’s Law
Particle Size Determination •
Coulter Counter
•
HIAC/Royco
•
Gelman Counter
Derived Properties Porosity of Voids •
Porosity – measure of a void volume in a powder material
•
Bulk Volume – total volume of the material
•
Void Volume – difference between bulk and true volume
Density
•
Ternary system
•
True Density – density of actual particle
•
2 liquids that are miscible + 3rd component (co-solvent) with affinity to both layers
•
Granule Density – volume of particles together with intraparticulate spaces
•
has 4 degrees of freedom
•
Bulk Density o mass of powder divided by the bulk volume o USP Method 1 – Graduated Cylinder o USP Method 2 – Scott Volumeter o USP Method 3 – Vessel
MICROMERITICS •
study of small particles
•
Fundamental properties o defined individually o Ex. particle size & shape, particle size distribution, surface area
•
Flow Properties •
Derived properties o computed o dependent on fundamental properties o Ex. Porosity, Density, Flow properties, Packing arrangement
Particle Size Determination Optical Microscopy
Angle of Response o maximum angle possible between the surface of a pile of power and the horizontal plane ℎ 𝑡𝑎𝑛𝜙 = 𝑟 h = height of cone r = radius of base cone o
•
↑ AOR = ↑ Flow Property
Tapped Density o measured using a tapped density tester by repeated tapping until a consistent tapped volume is achieved
•
microscope
•
individual particles can be seen
•
tedious and 2D image is only seen
•
Ferret Diameter – measure of the distance between tangents parallel to some fixed directions
LIQUIDS
•
Projected Area Diameter – diameter of a circle with the same area of the particle
•
less kinetic energy than gases
•
occupy definite volume
Martin Diameter – length of the line that bisects the particle
•
take the shape of contaniners
•
denser than gases
•
not compressible
•
Sieving •
use of sieves
•
official method – USP Method
•
mesh number refers to number of openings per inch
Solutions of Electrolytes & Non-Electrolytes True Solutions
•
↑ Mesh Number = ↓ Particle Size (inverse proportionality)
•
molecular dispersions
Lorenzo Dominick Cid 2015
•
particle size = <1nm
Electrolytes
Hypertonic Solutions •
more solutes compared to cell concentrations
•
freeze lower than -0.52°C
•
form ions in solution
•
causes creanation of the cell
•
electrical conductance
•
5% NaCl solution
•
Strong Electrolytes o completely ionized in solution o NaCl, HCl, H2SO4
Hypotonic Solutions
•
Weak Electrolytes o partial ionization o CH3COOH and most drugs
Non-Electrolytes •
do not form ions in solution
•
no electrical conductance
•
sucrose, glycerin, urea
Colligative Properties of Solutions Vapor Pressure Lowering •
pressure of saturated vapor above a liquid à escape of liquid molecules
•
non volatile solute + volatile solvent à decreased escape tendency
•
vapor pressure is lowered proportional to relative number of added solutes
•
Ex. Dextrose + Water à ↓VP of water
•
less solutes compared to cell concentrations
•
freeze higher than -0.52°C
•
causes lysis of the cell
•
distilled water
Methods of Adjusting Tonicity and pH •
Class I Methods o NaCl or some other subtance is added to the solution of the drug to make it isotonic
•
Freezing Point Depression/Crysoscopic Method o FPD used to calculate the amount of solute to add in making an isotonic solution
•
Class II Methods o water is added to the drug à isotonic solutions § White Vincent Method – V = w x E x 111.1 § Sprowls Method – V = 0.3g x E x 111.1
Theories of Acid & Bases Theory Arrhenius
Boiling Point Elevation •
temperature where VP of liquid = external atmospheric pressure
•
↑ non volatile solute in solution = ↑ BP of solution
Freezing Point Depression •
•
Base Liberates OH in aq. soln Proton acceptor Electron donor
Classification of Solvents •
Melting or Freezing Point o temp at which S & L phases are at equilibrium under 1 atm o indicator of purity
Protophillic (Basic Solvents) – capable of accepting protons from solute
•
Protogenic (Acidic Solvents) – proton donating
•
Aprotic – neither accepts nor donates
Solutions have ↓ FPD than pure substances
Ionization of Weak Acids & Bases
Osmotic Pressure •
Bronsted-Lowry Lewis
Acid Liberates H3O in aq. soln Proton donor Electron acceptor
pressure required to prevent the movement of water through a semipermeable membrane from region of high to low concentration
Tonicity of Solutions Isotonic Solutions •
living cell does not gain or loss water
•
same osmotic pressure with body fluids
•
0.9% NaCl solution, normal saline, D5W
•
Ionization – complete separation of ions in a crystal lattice when a salt is dissolved
•
Dissociation – separation of ions in solution when the ions are associated by interionic attraction
Henderson-Hasselbalch Equation •
aka pH or buffer equation
•
preparation of drug solutions at a desired pH using both the neutral and the salt forms of a drug
•
determine percentage of neutral and ionized forms at a given pH
•
determination of pKa of an acid or a base
Lorenzo Dominick Cid 2015
•
Surface & Interfacial Tension
For acid and its salt : [𝑠𝑎𝑙𝑡] 𝑝𝐻 = 𝑝𝐾𝑎 + log [𝑎𝑐𝑖𝑑]
•
For base and its salt : 𝑝𝐻 = 𝑝𝐾𝑎 + log
•
Interface Tension o force per unit length excisting at the interface between 2 immiscible liquids
Wetting Phenomenon
compound or a mixture of compounds which has the ability to resist changes in pH when small amounts of acids and bases are added
Buffer Capacity •
Surface Tension o force that pulls molecules of the interface together & contracts the surface
[𝑏𝑎𝑠𝑒] [𝑠𝑎𝑙𝑡]
Buffers •
•
•
angle that a droplet of the liquid makes with the solid surface at the point of
•
↑ Angle θ = ↓ wetting
•
180° = complete non wetting
SURFACTANTS (SURFACE ACTIVE AGENTS)
buffer efficiency or buffer index ∆𝐵 𝛽 = ∆𝑝𝐻
∆B = represents the small increment in gram equivalents per liter of strong base or acid added to the buffer solution to produce a change in pH
Solubility
•
long chain molecules
•
affinity for both polar and non polar solvents
•
reduces interfacial tension
•
based on Hydrophile –Lipophile Balance (HLB) Values Type
Anionic
Cationic
•
concentration of a saturated solution in which the dissolved solute is in equilibrium with its solid phase at constant
•
Intrinsic Solubility
•
Apparent Solubility
•
Kinetic Solubility
•
Thermodynamic Solubility
Amphoteric
Non-Ionic
Factors Affecting Solubility •
Dissolution Rate of Solute
•
Temperature
•
Addition of Salt
•
Complex Formation
•
Salt Formation
•
Amorphous Form
HLB Values 1-3
Descriptive Term
Parts of Solvent for One Part of Solute
Very soluble Freely Soluble Soluble Sparingly Soluble Slightly Soluble
<1 1-10 10-30 30-100 100-1000
Description
Examples
Long chain molecules of carboxylates, sulfates or sulfonates Interactions with negatively charged surfaces such as cell membranes; cytotoxic – antimicrobial preseratives Naturally occuring surfactants Zwitterions Long but contains a small alcohol base (eg. propylene glycol), sorbitan or glucerol to which fatty acids are attached to form fatty acid esters Utilities Antifoaming agent
3-6
W/O Emulsifying Agents
7-9
Wetting & Spreading Agents
8-18
O/W Emulsifying Agents
13-16
Detergents
15-20
Solubilizing
Sodium lauryl sulfate
Benzalkonium chloride
Polypeptides, Proteins Alkyl bentanes Lecithin, Cephalins Fatty alcohols (lauryl, cetyl, stearyl) Steroid alcohols Glyceril esters Examples Mineral Oil Fatty Alcohol Wax Span 80 Lanolin Brij 30 Docusate sodium Twean 20 Cremophor A25 Alkyl Benzenes Sulfonates Sodium Lauryl Sulfate
Interfacial Phenomenon •
attributed to the effect of the properties of molecules located or close to the boundary between immiscible phases
•
Interface – boundary between 2 distinct phases
Lorenzo Dominick Cid 2015
Electric Properties of Interfaces •
Nerst Potential – Electrothermodynamic
•
Zeta Potential – Electrokinetic
•
Streaming potential -- potential created by forcing a liquid to flow through a plug or bed of particles
COARSE DISPERSION
COLLOIDAL DISPERSIONS Lyophillic
•
Emulsion
•
Suspensions
•
Semisolid preparations – gels, jellies, suppositories & ointments
•
Solvent loving
•
dispersed phase consists generally or large organic molecules lying within a colloidal range
•
Molecules of the dispersed phase are solvated – they are associated with the molecule comprising the dispersion medium
Instability of Coarse Dispersion Emulsions •
Creaming – upward movement of internal phase
•
Spontaneously disperse to form colloidal dispersion
•
Sedimentation – downward movement of internal phase
•
thermodynamically stable
•
Flocculation – reversible aggregation of droplets
•
Coalescence/Cracking/Breaking – complete fusion of droplets (irreversible) Inversion – change in the type of emulsion (W/O à O/W or O/W à W/O)
Association •
Ampiphillic
•
•
dispersed phase consists of micelles or small organic molecules or ions whose size individually is below the colloidal range
Suspension
•
Hydrophillic or lipophillic portion is solvated – depending on whether the dispersion medium is aq. or non aq.
•
colloidal aggregates are formed spontaneously when the concentration of the ampiphile exceeds critical micelle concentration
Lyophobic •
solvent hating
•
dispersed phase consists of materials that have little attraction for the dispersion medium
•
material does not spontaneously form a dispersion
Properties of Colloids Kinetic Properties •
Brownian Movement – particles appear as tiny points of light in constant motion
•
Diffusion – movement of particles from high to low concentration until equilibrium is achieved
Optical Property •
Tyndall Effect – ability to scatter or disperse light
•
Faraday Effect
Electrokinetic Effect
•
Caking – compaction of suspended particles at the bottom of the container
Gels, Jellies, Suppositories & Ointments •
Syneresis – shirking of gel structure caused by loss of liquid
•
Bleeding – liberation of liquid from the base
•
Swelling/Imbibition – absorption of liquid into the structure
•
Swelling – increase in volume
•
Imbibition – no increase in volume
RHEOLOGY •
study of the flow of liquids
•
viscosity is the expression of the resistance of a fluid to flow
𝐹 𝐺 F = shearing stress (dyne/cm2) – amount of force per unit area required to cause a liquid to flow G = rate of shear (rev/min) – velocity of the system that leads to the deformation of the liquid 𝜂=
Viscosity Units of Measurement
•
Electrophoresis – movement of a charged particle through a liquid
•
Absolute viscosity – centipoise/poise
•
Kinematic viscosity – centistoke/stoke
•
Electroosmosis – movement of a liquid through plug or membrane across which a potential is applied
•
Relative viscosity – unitless
•
Sedimentation – creation of a potential when particles undergo sedimentation
Lorenzo Dominick Cid 2015
Measurement of Viscosity •
Dilatant Flow
Capillary Tube Viscometers o measure the time required for a given volume of liquid to flow through a capillary o o o
↑ Time = ↓ Viscosity Ex. Ostwald & Ubbelohde viscometers Follows Poiseulle’s Law :
𝜂 =
𝜋𝑟 ! 𝑡∆𝑃 8𝑙𝑣
r = radius of capillary t = time to flow P = pressure in dyne/cm2 l = length of capillary v = volume of liquid flowing •
Rotational Viscometers o makes use of a bob or spindle w/c is immersed in the in the liquid whose viscosity is to be determined o Rotating Bob – Brookfeil, Rotovisco, Stormer o Rotating Cup – MacMichael
Factors Affecting Viscosity •
Temperature o
↑T = ↓viscosity in liquids ; ↑ in gases
•
Shear Rate
•
Time
•
Concentration of Solution
Newtonian Systems •
direct relationship between shearing stress & rate
•
constant viscosity with increasing rate
•
eg. water, ethanol, acetone, glycerine, benzene
Non-Newtonian Systems Plastic Flow •
bingham bodies
•
curve does not through the origin but rather intersects the shearing stress axis at a particular point (yield value)
• •
•
shear thickening systems
•
reverse effects of pseudoplastic flow
•
viscosity increases with increases shear rate
•
Ex. starch in H2O, conc. suspension of inorganic pigments in H2O, Zinc Oxide, Barium sulfate or Titanium oxide in H2O
Thixotropy •
decrease in viscosity with time when flow is applied to a sample previously at rest and the recovery of viscosity in time when flow is continued
•
Ex. aq. bentonite magma
Rheopexy •
refers to the phenomenon that the gel formation of a system may be facilitated by tapping or low shear compared to keeping the sample at rest
•
time dependent increase in viscosity during flow
•
Ex. Bovine synovial fluid, serum albumin due to protein, Sodium hyalorunate
Antithixotropy •
time dependent increase in viscosity during flow caused by reversible aggregation of particles
•
reversed hysteresis loop
•
Ex. magnesia magma
GASES •
have kinetic energy that produces rapid motion
•
held together by weak intermolecular forces
•
capable of filling all available spaces
•
easily compressible
Gas Laws Gas Law
Equation
Constant Variable
Boyle’s Law
𝑃! 𝑉! = 𝑃! 𝑉!
Temperature
Gay-Lussac’s Law
Volume
a yeild value must be overcome before the system begins to flow
𝑃! 𝑃! = 𝑇! 𝑇!
Charles’ Law
Pressure
Ex. Flocculated suspension, gels, ointments, pastes, surfactants, polymeric substances
𝑉! 𝑉! = 𝑇! 𝑇!
Combined Gas Law
𝑃! 𝑉! 𝑃! 𝑉! = 𝑇! 𝑇!
Ideal Gas Equation
𝑃𝑉 = 𝑛𝑅𝑇
Pseudoplastic Flow •
shear thinning systems
•
curve begins at the origin
•
no yeild value
•
viscosity decreaes w/ increasing shear rate
•
Ex. Polymer solution, Na alginate, Perityl cellulose, PEG
Avogadro’s Principle •
equal volume of gases at constant temperature & pressure contain the same number of molecules
•
N – 6.02 x 1023 molecules/mole
Lorenzo Dominick Cid 2015
o o o
Ideal Gas Law •
no molecular interactions
•
elastic collisions
•
no exchange of energy
Photodegredation PV = nRT
n = number of mole/s (n = g/MW) R = molar gas constant 0.08205 L.atm/mole.K 1.987 cal/mole.K
Van der Waals Equation (P +
𝑎𝑛! )×( 𝑉 − 𝑛𝑏) = 𝑛𝑅𝑇 𝑣!
a = force of attraction between molecules b = size of molecules
•
sensitivity of drug to UV light
•
prevention à light resistant / opaque containers
Hydrolysis & Acid-Base Catalysis •
•
effect of pressure in solubility of a gas in liquid
•
in dilute solution, the partial vapor pressure of a solute is proportional to the mole ratio of the solute to that of the solvent in solution 𝑉2 𝑘𝑃! = 𝑉1 𝑃! P2 = partial vapor pressure of the has PT = total vapor pressure k = solubility coefficient
Graham’s Law
Reaction Rates •
may refer to the rate of degredation or formation of a product from a given reaction
•
velocity with which the reaction occurs
•
Influenced by: o Concentration o Temperature o Change in pH o Presence of additives o Presence of solvents o Radiation o Catalytic Agents or Enzymes
•
Order of Reactions Zero Order •
concentration independent kinetics
•
elimination of a reactant will be linear with time
•
Ex. suspension
•
speed of diffusion of 2 different gases is inversely proportionality to the square root of their densities
Raoult’s Law •
degredation of esters, amindes, lactams to carboxylic acid
CHEMICAL KINETICS
Henry’s Law
•
Chemical Properties and Composition Microbiological Sterility Therapeutic Activity
vapor pressure lowering due to effects of electrolytes or solutes in solution the partial vapor pressure of the solvent of an ideal solution is equal to the product of the mole fraction of the solvent and its vapor pressure in pure state 𝑃 = 𝑃! + 𝑃! PA = Vapor pressure x mole fraction of component A PB = Vapor pressure x mole fraction of component B MF of A + MF of B = 1
DRUG PRODUCT STABILITY •
extent to which a preparation retains the same properties that it had at the time of formulation
•
It is concerned with : o Physical Properties
First Order •
concentration dependent reaction
•
rate of reaction is proportional to the first power of the concentration of a single reacting species
•
most drugs follow such order of reaction
Second Order •
amount of drug is decresing at a rate proportional to the square of the amount of drug remaining
•
uncommon
Order Integrated Rate Law
Half Life
Unit of K
Zero Order 𝐴
First Order
Second Order
𝑙𝑛 𝐴 = 𝑙𝑛 𝐴 𝑜 − 𝑘𝑡
= 𝐴 𝑜 − 𝑘𝑡
𝑡!/! =
𝐴𝑜 2𝑘
𝑐𝑜𝑛𝑐. 𝑡𝑖𝑚𝑒
𝑡!/! =
0.683 𝑘
1 𝑡𝑖𝑚𝑒
1 1 = + 𝑘𝑡 [𝐴] 𝐴𝑜
𝑡!/! =
1 𝑘𝐴𝑜
𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛!! 𝑡𝑖𝑚𝑒 !!
Lorenzo Dominick Cid 2015
Lorenzo Dominick Cid 2015
Physical Pharmacy •
application of physical chemistry in pharmacy
•
study of physiochemical properties of substances used in drug formulation
FORCES OF ATTRACTION Intramolecular Forces •
forces of attraction within the molecule
•
Types – Ionic & Covalent Bonds o Ionic Bond § Transfer of electrons between a non metal & a metal § observed in formation of salts o Covalent Bond § sharing of electrons between two non metals § observed in organic compounds
Intramolecular Forces •
forces of attraction between molecules
•
Types – Binding & Attractive Forces o Binding Forces § Cohesion – similar molecules § Adhesion – different molecules § Repulsive – prevent molecules from annihilating each other o Attractive Forces § Van der Waals § Hydrogen Bond § Ion-Dipole § Ion-induced Dipole
Van der Waals Forces •
weak forces that involve the dispersion of charge across a molecule called a dipole o Keesom Forces (orientation effect) § Dipole-dipole § molecules are polar with permanent polar dipoles § Ex. water, HCl, ethanol, acetone, phenol o Debye Forces (induction effect) § Dipole-induced dipole § transient dipole induced by a permanent dipole § polar molecules produces temporary electric dipole in nonpolar molecules § Ex. Ethyl acetate, methylene chloride, ether o London Forces (dispersion effect) § Induced dipole- induced dipole § induce polarity between non polar molecules
responsible for liquefaction of gases Ex. Carbon disulfide, CCl2, hexane
Hydrogen Bond •
electrostatic interaction of H with highly electronegative atoms (S,N,Cl,F,O)
•
s for unusual properties of water
Ion-Dipole Interaction •
polar molecules are attracted to either positive or negative charges
•
occurs when salt is dissolved in a polar solvent
•
solubility if crystalline substances in H2O
•
quaternary ammonium + tertiary amine
Ion-Induced Dipole •
induced by close proximity of a charged ion to a non polar molecule
•
responsible for the solubility of non polar molecules
•
Ex. Iodine complex with salts
PHYSICAL PROPERTIES OF MATTER Additive •
depends on the total contribution of the atoms in the molecules
•
Ex. MW, Mass
•
↑ atoms = ↑MW = ↑Mass
Constitutive •
depends on the arrangement of the number & kind of atoms within a molecule
•
Ex. Refactive Index, Optical Rotation
Colligative •
function of the number of species or particles present in a given solution
•
Ex. Osmotic pressure elevation, Vapor Pressure lowering, Freezing Point Depression, Boiling Point Elevation
TYPES OF PROPERTIES Intensive •
independent of the amount of the substance in the system
•
Ex. Temperature, Pressure, Density, Viscosity, Surface tension, Specific Gravity
Extensive •
depends on the quantity of substance in the system
•
Ex. Mass, Length, Volume
Lorenzo Dominick Cid 2015
P1 & P2 = vapor pressures at T1 & T2 ∆Hv = molar heat of vaporization R = 1.987 cal/mole deg
STATES OF MATTER The Gaseous State Gas Laws •
refers to an ideal situation where no intermolecular interactions exist and collisions are perfectly elastic
•
there is no energy exchanged upon collision
•
Boyle’s Law o relates volume and pressure o constant temperature o PV = k
•
•
Gay-Lussac and Charles’ Law o states that the volume and absolute temperature of a gas at constant pressure are directly proportional o V = kT Ideal Gas Law o PV = nRT o R = 0.08205 liter.atm/mole.K or 8.314 joules/mole.K or 1.987 cal/mole deg o n = number of moles
The Solid State •
have fixed shapes
•
nearly incompressible
•
have strong intermolecular forces
•
very little kinetic energy
•
atoms vibrate fixed positions about an equilibrium position, & so there is very little transitional motion
Crystalline Solids •
Solids whose structural units are arranged in a fixed geometric pattern or lattices
•
definite shape
•
orderly arrangement of units
•
definite and sharp melting points
•
6 Distinct Critical Systems Based on Symmetry o Cubic – Sodium Chloride o Tetragonal – Urea o Hexagonal – Iodoform o Monoclinic – Sucrose o Rhombic – I2 o Triclinic – Boric Acid
Kinetic Molecular Theory •
Gases are composed of particles called atoms or molecules, the total volume of which is so small as to be negligible in relation to the volume of the space in which the molecules are confined
•
The particles of the gas do not attract one another, but instead move with complete independence
•
The particles exhibit continuous random motion owing to their kinetic energy
•
glasses or supercooled liquids
•
molecules are arranged in a random manner
The molecules exhibit perfect elasticity
•
no definite melting points
•
faster dissolution rate
•
The Liquid State • •
• •
Critical temperature – temperature above which a liquid can no longer exist Critical Pressure o pressure required to liquefy a gas a critical temperature o highest vapor pressure of a liquid
Polymorphism •
condition where substances can exist in more than 1 crystalline form
•
polymorphs have different melting points, x-ray crystals and diffraction patterns and solubility
•
Theobroma Oil Polymorphs (Melting Points)
Boiling Point – the temp at which the vapor pressure of the liquid equals the external and atmospheric pressure
o
Unstable γ form à 18°C
o
α form à 22°C
Latent Heat of Vaporization o the quantity of heat taken up when a liquid vaporizes o it is liberated when a vapor condenses with a liquid
o
β prime form à 28°C
o
Stable β form à 34°C
Clausius-Clapeyron Equation •
Amorphous Solids
relationship of vapor pressure and absolute temperature of a liquid
log
•
Types of Polymorphism o Enantiotropic – reversible o Monotropic – unidirectional transition
Freezing Point •
temperature at which liquid à solid
•
melting point of a pure crystalline compound
P1 ∆Hv (T2 -T1 ) = P2 2.303 RT1 T2
Lorenzo Dominick Cid 2015
Latent Heat of Fusion •
Energy absorbed when 1g of a solid melts
•
Heat liberated when it freezes
Liquid Crystalline State •
liquid crystals à intermediate between liquid and solid states
•
may result from the heating of solids (thermotropic) or from the action of certain solvents on solids (lyotropic liquid crystals)
Two Main Types of Liquid Crystals •
•
Smectic o Soaplike or greaselike o molecules are mobile in 2 directions o rotates in 1 axis Nematic o o o o
threadlike molecules are mobile in 3 directions rotates in 1 axis Cholesteric – special type of nematic
Supercritical Fluids
THERMODYNAMICS •
deals with the quantitative relationships of interconversion of the various forms of energy
•
System – a well defined part of the universe under study
•
Surroundings – the rest of the universe from which the observations are made
•
Boundaries – physical or virtual barriers that separate a system from the surroundings
Types of Systems •
Open – energy and matter can be exchanged with the surroundings
•
Closed – energy can be exchange with the surroundings but not matter
•
Isolated – neither matter not energy can be exchanged with the surroundings
First Law of Thermodynamics •
Energy cannot be created nor destroyed, it can only be transformed into a different form
•
Adiabatic – constant heat
•
Isothermic – constant temperature Isochoric – constant volume Isobaric – constant pressure
•
properties intermediate between those of liquids and gases
•
•
formed from the gaseous state where the gas is held under a combination of temperatures and pressures that exceed the critical point of a substance
•
Second Law of Thermodynamics •
Refers to the probability of the occurrence of a process based on the tendency of a system to approach a state of energy equilibrium
•
Entropy
THE PHASE RULE (GIBB’S PHASE RULE) •
relates the effect of the least number of independent variables (T, P & C) among the various phases (S,L & G) that can exist in an equilibrium system containing a given number of components
Third Law of Thermodynamics •
𝐹 =𝐶−𝑃+𝑋 F = no. of degrees of freedom C = no. chemical components P = no. of phases X = variable dependent upod considerations of the phase diagram •
F – least number of intensive/independent variables that must be fixed to describe the system completely
•
C – smallest number of constituents by which the composition of each pase in the system at equilibrium can be expressed in the form of a chemical formula or equation
•
P – number of homogenous physically distinct portion of a system that is seperated from other portions of the system by bounding surfaces
•
1 Phase – F=2 – Bivariant
•
2 Phases – F=1 – Univariant
•
3 Phases – F=0 – Invariant
The entropy of a pure crystalline substance is zero at absolute zero because the crystal arrangement must show the greatest orderliness at this temperature
CONDENSED SYSTEMS •
S & L phases only
•
the vapor state is disregarded with an assumption of working at a pressure at 1atm o 2 Components – liquid phases o 2 Components – S & L – eutectic mixtures o 3 Components
Two Component System Containing Two Liquids •
Binodal Curve – area within the curve which represent a 2 phase system
•
Upper Consolute/Critical Solution Temperature – max. temperature at which two phase region in the phase diagram of a two-component system containing two liquids will exist
Lorenzo Dominick Cid 2015
•
Tie line o o
•
Sedimentation line from which a system seperates into phases of constant composition approximates proportion of components in a particular temperature
Conjugate Phases o phases of constant composition that separate when a mixture is prepared within the boundary of the 2phase system
Two Component System Containing Solid and Liquid •
Eutectic Point o minimum temp. where both exist in liquid form o point where solid A, solid B & the liquid phase coexist
Three Component System
•
Andreasen apparatus
•
↑ Sedimentation rate = ↑ Particle size (direct proportionality)
•
follow the Stoke’s Law
Particle Size Determination •
Coulter Counter
•
HIAC/Royco
•
Gelman Counter
Derived Properties Porosity of Voids •
Porosity – measure of a void volume in a powder material
•
Bulk Volume – total volume of the material
•
Void Volume – difference between bulk and true volume
Density
•
Ternary system
•
True Density – density of actual particle
•
2 liquids that are miscible + 3rd component (co-solvent) with affinity to both layers
•
Granule Density – volume of particles together with intraparticulate spaces
•
has 4 degrees of freedom
•
Bulk Density o mass of powder divided by the bulk volume o USP Method 1 – Graduated Cylinder o USP Method 2 – Scott Volumeter o USP Method 3 – Vessel
MICROMERITICS •
study of small particles
•
Fundamental properties o defined individually o Ex. particle size & shape, particle size distribution, surface area
•
Flow Properties •
Derived properties o computed o dependent on fundamental properties o Ex. Porosity, Density, Flow properties, Packing arrangement
Particle Size Determination Optical Microscopy
Angle of Response o maximum angle possible between the surface of a pile of power and the horizontal plane ℎ 𝑡𝑎𝑛𝜙 = 𝑟 h = height of cone r = radius of base cone o
•
↑ AOR = ↑ Flow Property
Tapped Density o measured using a tapped density tester by repeated tapping until a consistent tapped volume is achieved
•
microscope
•
individual particles can be seen
•
tedious and 2D image is only seen
•
Ferret Diameter – measure of the distance between tangents parallel to some fixed directions
LIQUIDS
•
Projected Area Diameter – diameter of a circle with the same area of the particle
•
less kinetic energy than gases
•
occupy definite volume
Martin Diameter – length of the line that bisects the particle
•
take the shape of contaniners
•
denser than gases
•
not compressible
•
Sieving •
use of sieves
•
official method – USP Method
•
mesh number refers to number of openings per inch
Solutions of Electrolytes & Non-Electrolytes True Solutions
•
↑ Mesh Number = ↓ Particle Size (inverse proportionality)
•
molecular dispersions
Lorenzo Dominick Cid 2015
•
particle size = <1nm
Electrolytes
Hypertonic Solutions •
more solutes compared to cell concentrations
•
freeze lower than -0.52°C
•
form ions in solution
•
causes creanation of the cell
•
electrical conductance
•
5% NaCl solution
•
Strong Electrolytes o completely ionized in solution o NaCl, HCl, H2SO4
Hypotonic Solutions
•
Weak Electrolytes o partial ionization o CH3COOH and most drugs
Non-Electrolytes •
do not form ions in solution
•
no electrical conductance
•
sucrose, glycerin, urea
Colligative Properties of Solutions Vapor Pressure Lowering •
pressure of saturated vapor above a liquid à escape of liquid molecules
•
non volatile solute + volatile solvent à decreased escape tendency
•
vapor pressure is lowered proportional to relative number of added solutes
•
Ex. Dextrose + Water à ↓VP of water
•
less solutes compared to cell concentrations
•
freeze higher than -0.52°C
•
causes lysis of the cell
•
distilled water
Methods of Adjusting Tonicity and pH •
Class I Methods o NaCl or some other subtance is added to the solution of the drug to make it isotonic
•
Freezing Point Depression/Crysoscopic Method o FPD used to calculate the amount of solute to add in making an isotonic solution
•
Class II Methods o water is added to the drug à isotonic solutions § White Vincent Method – V = w x E x 111.1 § Sprowls Method – V = 0.3g x E x 111.1
Theories of Acid & Bases Theory Arrhenius
Boiling Point Elevation •
temperature where VP of liquid = external atmospheric pressure
•
↑ non volatile solute in solution = ↑ BP of solution
Freezing Point Depression •
•
Base Liberates OH in aq. soln Proton acceptor Electron donor
Classification of Solvents •
Melting or Freezing Point o temp at which S & L phases are at equilibrium under 1 atm o indicator of purity
Protophillic (Basic Solvents) – capable of accepting protons from solute
•
Protogenic (Acidic Solvents) – proton donating
•
Aprotic – neither accepts nor donates
Solutions have ↓ FPD than pure substances
Ionization of Weak Acids & Bases
Osmotic Pressure •
Bronsted-Lowry Lewis
Acid Liberates H3O in aq. soln Proton donor Electron acceptor
pressure required to prevent the movement of water through a semipermeable membrane from region of high to low concentration
Tonicity of Solutions Isotonic Solutions •
living cell does not gain or loss water
•
same osmotic pressure with body fluids
•
0.9% NaCl solution, normal saline, D5W
•
Ionization – complete separation of ions in a crystal lattice when a salt is dissolved
•
Dissociation – separation of ions in solution when the ions are associated by interionic attraction
Henderson-Hasselbalch Equation •
aka pH or buffer equation
•
preparation of drug solutions at a desired pH using both the neutral and the salt forms of a drug
•
determine percentage of neutral and ionized forms at a given pH
•
determination of pKa of an acid or a base
Lorenzo Dominick Cid 2015
•
Surface & Interfacial Tension
For acid and its salt : [𝑠𝑎𝑙𝑡] 𝑝𝐻 = 𝑝𝐾𝑎 + log [𝑎𝑐𝑖𝑑]
•
For base and its salt : 𝑝𝐻 = 𝑝𝐾𝑎 + log
•
Interface Tension o force per unit length excisting at the interface between 2 immiscible liquids
Wetting Phenomenon
compound or a mixture of compounds which has the ability to resist changes in pH when small amounts of acids and bases are added
Buffer Capacity •
Surface Tension o force that pulls molecules of the interface together & contracts the surface
[𝑏𝑎𝑠𝑒] [𝑠𝑎𝑙𝑡]
Buffers •
•
•
angle that a droplet of the liquid makes with the solid surface at the point of
•
↑ Angle θ = ↓ wetting
•
180° = complete non wetting
SURFACTANTS (SURFACE ACTIVE AGENTS)
buffer efficiency or buffer index ∆𝐵 𝛽 = ∆𝑝𝐻
∆B = represents the small increment in gram equivalents per liter of strong base or acid added to the buffer solution to produce a change in pH
Solubility
•
long chain molecules
•
affinity for both polar and non polar solvents
•
reduces interfacial tension
•
based on Hydrophile –Lipophile Balance (HLB) Values Type
Anionic
Cationic
•
concentration of a saturated solution in which the dissolved solute is in equilibrium with its solid phase at constant
•
Intrinsic Solubility
•
Apparent Solubility
•
Kinetic Solubility
•
Thermodynamic Solubility
Amphoteric
Non-Ionic
Factors Affecting Solubility •
Dissolution Rate of Solute
•
Temperature
•
Addition of Salt
•
Complex Formation
•
Salt Formation
•
Amorphous Form
HLB Values 1-3
Descriptive Term
Parts of Solvent for One Part of Solute
Very soluble Freely Soluble Soluble Sparingly Soluble Slightly Soluble
<1 1-10 10-30 30-100 100-1000
Description
Examples
Long chain molecules of carboxylates, sulfates or sulfonates Interactions with negatively charged surfaces such as cell membranes; cytotoxic – antimicrobial preseratives Naturally occuring surfactants Zwitterions Long but contains a small alcohol base (eg. propylene glycol), sorbitan or glucerol to which fatty acids are attached to form fatty acid esters Utilities Antifoaming agent
3-6
W/O Emulsifying Agents
7-9
Wetting & Spreading Agents
8-18
O/W Emulsifying Agents
13-16
Detergents
15-20
Solubilizing
Sodium lauryl sulfate
Benzalkonium chloride
Polypeptides, Proteins Alkyl bentanes Lecithin, Cephalins Fatty alcohols (lauryl, cetyl, stearyl) Steroid alcohols Glyceril esters Examples Mineral Oil Fatty Alcohol Wax Span 80 Lanolin Brij 30 Docusate sodium Twean 20 Cremophor A25 Alkyl Benzenes Sulfonates Sodium Lauryl Sulfate
Interfacial Phenomenon •
attributed to the effect of the properties of molecules located or close to the boundary between immiscible phases
•
Interface – boundary between 2 distinct phases
Lorenzo Dominick Cid 2015
Electric Properties of Interfaces •
Nerst Potential – Electrothermodynamic
•
Zeta Potential – Electrokinetic
•
Streaming potential -- potential created by forcing a liquid to flow through a plug or bed of particles
COARSE DISPERSION
COLLOIDAL DISPERSIONS Lyophillic
•
Emulsion
•
Suspensions
•
Semisolid preparations – gels, jellies, suppositories & ointments
•
Solvent loving
•
dispersed phase consists generally or large organic molecules lying within a colloidal range
•
Molecules of the dispersed phase are solvated – they are associated with the molecule comprising the dispersion medium
Instability of Coarse Dispersion Emulsions •
Creaming – upward movement of internal phase
•
Spontaneously disperse to form colloidal dispersion
•
Sedimentation – downward movement of internal phase
•
thermodynamically stable
•
Flocculation – reversible aggregation of droplets
•
Coalescence/Cracking/Breaking – complete fusion of droplets (irreversible) Inversion – change in the type of emulsion (W/O à O/W or O/W à W/O)
Association •
Ampiphillic
•
•
dispersed phase consists of micelles or small organic molecules or ions whose size individually is below the colloidal range
Suspension
•
Hydrophillic or lipophillic portion is solvated – depending on whether the dispersion medium is aq. or non aq.
•
colloidal aggregates are formed spontaneously when the concentration of the ampiphile exceeds critical micelle concentration
Lyophobic •
solvent hating
•
dispersed phase consists of materials that have little attraction for the dispersion medium
•
material does not spontaneously form a dispersion
Properties of Colloids Kinetic Properties •
Brownian Movement – particles appear as tiny points of light in constant motion
•
Diffusion – movement of particles from high to low concentration until equilibrium is achieved
Optical Property •
Tyndall Effect – ability to scatter or disperse light
•
Faraday Effect
Electrokinetic Effect
•
Caking – compaction of suspended particles at the bottom of the container
Gels, Jellies, Suppositories & Ointments •
Syneresis – shirking of gel structure caused by loss of liquid
•
Bleeding – liberation of liquid from the base
•
Swelling/Imbibition – absorption of liquid into the structure
•
Swelling – increase in volume
•
Imbibition – no increase in volume
RHEOLOGY •
study of the flow of liquids
•
viscosity is the expression of the resistance of a fluid to flow
𝐹 𝐺 F = shearing stress (dyne/cm2) – amount of force per unit area required to cause a liquid to flow G = rate of shear (rev/min) – velocity of the system that leads to the deformation of the liquid 𝜂=
Viscosity Units of Measurement
•
Electrophoresis – movement of a charged particle through a liquid
•
Absolute viscosity – centipoise/poise
•
Kinematic viscosity – centistoke/stoke
•
Electroosmosis – movement of a liquid through plug or membrane across which a potential is applied
•
Relative viscosity – unitless
•
Sedimentation – creation of a potential when particles undergo sedimentation
Lorenzo Dominick Cid 2015
Measurement of Viscosity •
Dilatant Flow
Capillary Tube Viscometers o measure the time required for a given volume of liquid to flow through a capillary o o o
↑ Time = ↓ Viscosity Ex. Ostwald & Ubbelohde viscometers Follows Poiseulle’s Law :
𝜂 =
𝜋𝑟 ! 𝑡∆𝑃 8𝑙𝑣
r = radius of capillary t = time to flow P = pressure in dyne/cm2 l = length of capillary v = volume of liquid flowing •
Rotational Viscometers o makes use of a bob or spindle w/c is immersed in the in the liquid whose viscosity is to be determined o Rotating Bob – Brookfeil, Rotovisco, Stormer o Rotating Cup – MacMichael
Factors Affecting Viscosity •
Temperature o
↑T = ↓viscosity in liquids ; ↑ in gases
•
Shear Rate
•
Time
•
Concentration of Solution
Newtonian Systems •
direct relationship between shearing stress & rate
•
constant viscosity with increasing rate
•
eg. water, ethanol, acetone, glycerine, benzene
Non-Newtonian Systems Plastic Flow •
bingham bodies
•
curve does not through the origin but rather intersects the shearing stress axis at a particular point (yield value)
• •
•
shear thickening systems
•
reverse effects of pseudoplastic flow
•
viscosity increases with increases shear rate
•
Ex. starch in H2O, conc. suspension of inorganic pigments in H2O, Zinc Oxide, Barium sulfate or Titanium oxide in H2O
Thixotropy •
decrease in viscosity with time when flow is applied to a sample previously at rest and the recovery of viscosity in time when flow is continued
•
Ex. aq. bentonite magma
Rheopexy •
refers to the phenomenon that the gel formation of a system may be facilitated by tapping or low shear compared to keeping the sample at rest
•
time dependent increase in viscosity during flow
•
Ex. Bovine synovial fluid, serum albumin due to protein, Sodium hyalorunate
Antithixotropy •
time dependent increase in viscosity during flow caused by reversible aggregation of particles
•
reversed hysteresis loop
•
Ex. magnesia magma
GASES •
have kinetic energy that produces rapid motion
•
held together by weak intermolecular forces
•
capable of filling all available spaces
•
easily compressible
Gas Laws Gas Law
Equation
Constant Variable
Boyle’s Law
𝑃! 𝑉! = 𝑃! 𝑉!
Temperature
Gay-Lussac’s Law
Volume
a yeild value must be overcome before the system begins to flow
𝑃! 𝑃! = 𝑇! 𝑇!
Charles’ Law
Pressure
Ex. Flocculated suspension, gels, ointments, pastes, surfactants, polymeric substances
𝑉! 𝑉! = 𝑇! 𝑇!
Combined Gas Law
𝑃! 𝑉! 𝑃! 𝑉! = 𝑇! 𝑇!
Ideal Gas Equation
𝑃𝑉 = 𝑛𝑅𝑇
Pseudoplastic Flow •
shear thinning systems
•
curve begins at the origin
•
no yeild value
•
viscosity decreaes w/ increasing shear rate
•
Ex. Polymer solution, Na alginate, Perityl cellulose, PEG
Avogadro’s Principle •
equal volume of gases at constant temperature & pressure contain the same number of molecules
•
N – 6.02 x 1023 molecules/mole
Lorenzo Dominick Cid 2015
o o o
Ideal Gas Law •
no molecular interactions
•
elastic collisions
•
no exchange of energy
Photodegredation PV = nRT
n = number of mole/s (n = g/MW) R = molar gas constant 0.08205 L.atm/mole.K 1.987 cal/mole.K
Van der Waals Equation (P +
𝑎𝑛! )×( 𝑉 − 𝑛𝑏) = 𝑛𝑅𝑇 𝑣!
a = force of attraction between molecules b = size of molecules
•
sensitivity of drug to UV light
•
prevention à light resistant / opaque containers
Hydrolysis & Acid-Base Catalysis •
•
effect of pressure in solubility of a gas in liquid
•
in dilute solution, the partial vapor pressure of a solute is proportional to the mole ratio of the solute to that of the solvent in solution 𝑉2 𝑘𝑃! = 𝑉1 𝑃! P2 = partial vapor pressure of the has PT = total vapor pressure k = solubility coefficient
Graham’s Law
Reaction Rates •
may refer to the rate of degredation or formation of a product from a given reaction
•
velocity with which the reaction occurs
•
Influenced by: o Concentration o Temperature o Change in pH o Presence of additives o Presence of solvents o Radiation o Catalytic Agents or Enzymes
•
Order of Reactions Zero Order •
concentration independent kinetics
•
elimination of a reactant will be linear with time
•
Ex. suspension
•
speed of diffusion of 2 different gases is inversely proportionality to the square root of their densities
Raoult’s Law •
degredation of esters, amindes, lactams to carboxylic acid
CHEMICAL KINETICS
Henry’s Law
•
Chemical Properties and Composition Microbiological Sterility Therapeutic Activity
vapor pressure lowering due to effects of electrolytes or solutes in solution the partial vapor pressure of the solvent of an ideal solution is equal to the product of the mole fraction of the solvent and its vapor pressure in pure state 𝑃 = 𝑃! + 𝑃! PA = Vapor pressure x mole fraction of component A PB = Vapor pressure x mole fraction of component B MF of A + MF of B = 1
DRUG PRODUCT STABILITY •
extent to which a preparation retains the same properties that it had at the time of formulation
•
It is concerned with : o Physical Properties
First Order •
concentration dependent reaction
•
rate of reaction is proportional to the first power of the concentration of a single reacting species
•
most drugs follow such order of reaction
Second Order •
amount of drug is decresing at a rate proportional to the square of the amount of drug remaining
•
uncommon
Order Integrated Rate Law
Half Life
Unit of K
Zero Order 𝐴
First Order
Second Order
𝑙𝑛 𝐴 = 𝑙𝑛 𝐴 𝑜 − 𝑘𝑡
= 𝐴 𝑜 − 𝑘𝑡
𝑡!/! =
𝐴𝑜 2𝑘
𝑐𝑜𝑛𝑐. 𝑡𝑖𝑚𝑒
𝑡!/! =
0.683 𝑘
1 𝑡𝑖𝑚𝑒
1 1 = + 𝑘𝑡 [𝐴] 𝐴𝑜
𝑡!/! =
1 𝑘𝐴𝑜
𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛!! 𝑡𝑖𝑚𝑒 !!
Lorenzo Dominick Cid 2015
Lorenzo Dominick Cid 2015
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