physical Pharmacy

• Vapor pressure lowering

• Boiling point elevation

• Freezing point depression

• Osmotic pressure

What are the colligative properties of liquids?

Boiling point

temperature where VP of liquid = external atmospheric pressure

Freezing point depression

• temperature at which S & L phases are at equilibrium

• under 1 atm indicator of purity

Osmotic pressure

pressure required to prevent the movement of water through a semipermeable membrane from region of high to low concentration

True Solutions

Molecular dispersions with particle sizes less than 1 nm.

Electrolytes

Substances that form ions in solution and provide electrical conductivity.

Strong Electrolytes

Substances that completely ionize in solution, such as NaCl, HCl, and H2SO4.

Weak Electrolytes

Substances that partially ionize in solution, like CH3COOH and most drugs.

Non-Electrolytes

Substances that do not form ions in solution, such as sucrose and glycerin.

Isotonic Solutions

Solutions where the living cell does not gain or lose water; have the same osmotic pressure as bodily fluids, e.g., 0.9% NaCl solution, normal saline, D5W.

Hypertonic Solutions

Solutions with more solute compared to cell concentrations, causing crenation of the cell.

Hypotonic Solutions

Solutions with less solute compared to cell concentrations, leading to swelling of the cell.

Class I Methods

Methods where other substances are added to the solution to adjust tonicity and pH.

Freezing Point Depression/Cryoscopic Method

Method used to calculate the amount of solute to add in an isotonic solution.

Arhenius Theory

Acids liberate H2O in aqueous solutions, while bases liberate OH-.

Bronsted-Lowry Theory

Acids are proton donors and bases are proton acceptors.

Lewis Theory

Acids are electron pair acceptors and bases are electron pair donors.

Photophilic Solvents

Basic solvents capable of accepting protons from solute.

Proteogenic Solvents

Acidic solvents that donate protons.

Aprotic Solvents

Solvents that neither accept nor donate protons.

Henderson-Hasselbalch Equation

Used for pH or buffer calculation and determining the pKa of acids and bases.

Weak Acids

Acids that do not completely ionize in solution.

Weak Bases

Bases that do not completely ionize in solution.

Buffers

A compound or mixture that resists changes in pH when small amounts of acids or bases are added.

Solubility

Concentratino of solute in a saturated solution at given temperatur

• <1

• 1-10

• 10-30

• 30-10

• 100-1000

• 1000-10000

• >10000

Interfacial phenomenon

Attributed to the effect of the properties of molecules located or close to the boundary between immiscible phases.

Surface tension

Force that pulls molecules of the interface together and contracts the surface.

Interface tension

Force per unit length existing at the interface between two immiscible liquids.

Wetting phenomenon

Contact angle at which a droplet of the liquid makes with the solid surface at the point of contact.

• > 90°

• < 90°

Contact angle:

• — indicates non-wetting.

• — indicates wetting.

Surfactants

Surface active agents that reduce surface tension between liquids or between a liquid and a solid.

Hydrophilic and lipophilic balance (HLB)

Determines the properties of surfactants; influences their solubility in different environments.

Anionic surfactants

Surfactants with negatively charged head groups, e.g., Sodium lauryl sulfate.

Cationic surfactants

Surfactants with positively charged head groups, e.g., Benzalkonium chloride.

Non-ionic surfactants

Surfactants that do not carry charge, e.g., Glyceryl esters.

Amphoteric surfactants

Surfactants that can carry both positive and negative charges depending on the pH.

Recall

Recall HLB Values

Brownian Movement

Particles appear to sway at random; points of least resistance.

Electrophoresis

Movement of a charged particle through a solution.

Electroosmosis

Movement of liquid through plug or porous barrier.

Searing Potential

Potential created by forcing a liquid to flow through a pair of particles.

Lyophilic

Solvent loving; dispersed phase consists generally of large organic molecules. Molecules of the dispersed phase are solvolated - they are associated with the molecule comprising the dispersion medium. Spontaneously disperse to form colloidal dispersion thermodynamically stable.

Amphiphilic

Dispersed phase consists of micelles or small organic molecules or ions whose size individually is below the colloidal range. Hydrophilic or lipophilic portion is solvate - depending on whether the dispersion medium is, or is not, an organic solvent, the amphiphile exerts critical micelle concentration.

Lyophobic

Solvent hating; dispersed phase consists of materials that have little affinity for the dispersion medium. The material does not spontaneously form a dispersion.

• Emulsion

• Suspensions

• SSDs (gels, jellies, suppositories, oints)

What are examples of coarse dispersions

Creaming

Upward movement of internal phase.

Sedimentation

Downward movement of internal phase.

Flocculation

Reversible aggregation of droplets.

Coalescence/Cracking/Breaking

Complete fusion of droplets (irreversible).

Inversion

Change in the type of emulsion (W/O ↔ O/W).

Caking

Compaction of suspended particles at the bottom of the container.

Syneresis

Shrinking of gel structure caused by loss of liquid.

Bleeding

Liberation of liquid from the base.

Swelling

Increase in volume.

Imbibition

No increase in volume

Rheology

Study of the flow of liquids.

F = shearing stress (dynamic)

Amount of force per unit area required to cause a fluid to flow.

G = rate of shear (dynamic)

Velocity of the system that leads to the deformation of the liquid.

Intramolecular Forces

Forces of attraction within the molecule.

Ionic Bond

Transfer of electrons between a non-metal and a metal observed in formation of salts.

Covalent Bond

Sharing of electrons between two non-metals, observed in organic compounds.

Intermolecular Forces

Forces of attraction between molecules.

Cohesion

Attractive forces between similar molecules.

Adhesion

Attractive forces between different molecules.

Repulsive Forces

Forces that prevent molecules from annihilating each other.

Van der Waals Forces

Weak forces that involve the dispersion of charge across a molecule called a dipole.

Keesom forces (orientation effect)

• Attractive forces between permanent polar dipoles.

• Interactions between polar molecules with permanent dipoles.

• Ex. water, HCl, ethanol, acetone, phenol

Hydrogen Bond

Electrostatic interaction of hydrogen with highly electronegative atoms (S, Cl, N, O, F).

Debye Forces (induction effect)

• Dipole-induced dipole

• transient dipole induced by a permanent dipole

• olar molecules produce temporary electric dipole in nonpolar molecules

• Ex. Ethyl acetate, methylene chloride, ether

London Forces (dispersion effect)

Ion-Dipole Interaction

Polar molecules are attracted to either positive or negative charges; occurs when salt is dissolved in a polar solvent; affects solubility if crystalline substances in water, as seen with quaternary ammonium and 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

Additive

Depends on the total contribution of the atoms in the molecules. Ex. MW, Mass

Constitutive

Depends on the arrangement of the number & kind of atoms within a molecule. Ex. Refractive 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

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

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

Relates volume and pressure at constant temperature. Formula: PV = k.

Gay-Lussac and Charles' Law

States that the volume and absolute temperature of a gas at constant pressure are directly proportional. Formula: V = kT.

Ideal Gas Law

Expressed as PV = nRT, where P = pressure, V = volume, n = number of moles, R = ideal gas constant.

Kinetic Molecular Theory

Gases are composed of particles called atoms or molecules; they exhibit continuous random motion and do not attract one another, leading to complete independence.

Critical temperature

temperature above which a liquid can no longer exist

Critical pressure

pressure required to liquefy a gas a critical temperature highest vapor pressure of a liquid

Boiling point

the temp at which the vapor pressure of the liquid equals the external and atmospheric pressure

Solid State

Solids have fixed shapes, are nearly incompressible, and exhibit strong intermolecular forces.

Crystalline Solids

Solids whose structural units are arranged in a definite geometric pattern or lattice, having defined shapes and sharp melting points.

Amorphous Solids

Solids with no defined shape; molecules are arranged randomly, resulting in gradual melting instead of sharp melting points.

Polymorphism

Condition where substances can exist in more than one crystalline form, affecting their melting points and stability.

Freezing Point

The temperature at which a liquid becomes solid, corresponding to the equilibrium between solid and liquid phases.

Latent Heat of Fusion

The energy required to convert 1 gram of a solid into a liquid without a change in temperature.

Liquid Crystals

Intermediate between liquid and solid states, often resulting from heating of solids (thermotropic) or action of solvents on solids (lyotropic).

Smectic Liquid Crystals

Molecules are mobile in two directions and rotate in one axis. Ex. soap-like or grease-like.

Nematic Liquid Crystals

Molecules are mobile in three directions and rotate in one axis. Ex. threadlike; cholesteric is a special type of nematic.

Phase Rule (Gibbs Phase Rule)

Relates the effect of the least number of independent variables (F, P, & C) among the various phases (S, L, & G) that can exist in an equilibrium system containing a given number of components.

F = C - P + 2 or X

What is the phase rule equation

Thermodynamics

Thermodynamics deals with the quantitative relationships of the interconversion of the various forms of energy.

System

A system is a well-defined part of the universe under study.

Surroundings

Surroundings refer to the rest of the universe from which the system gains or loses energy.