Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
SM
Uploaded byShubhrat Maheshwari
12,580 views

Introduction of solubilty, solubility expression, solute solvent interaction.pdf

This document discusses the solubility of drugs, including definitions and terms related to solubility. It defines solubility as the concentration of a substance that dissolves in a given volume of solvent at a certain temperature. Solubility depends on properties of the solvent and solute as well as temperature, pressure, and pH. The document also discusses quantitative and descriptive expressions of solubility, such as molarity and mole fraction. Finally, it examines the mechanisms of solute-solvent interactions, including factors like polarity, hydrogen bonding, and relative strengths of solvent-solvent, solute-solute, and solvent-solute interactions.

Education◦
SOLUBILITY OF DRUGS SOLUBILITY EXPRESSION, MECHANISM OF SOLUTE-SOLVENT INTERACTION Presented by – Mr Shubhrat Maheshwari Assistant Professor, Faculty of Pharmaceutical Sciences, Rama University Kanpur
Solubility of Drugs • Solubility is defined as the concentration of a substance (solute) that dissolves in a given volume of solution (solvent) at a certain temperature to form a spontaneous solution of solute in the solvent. • Solubility can also be defined as the spontaneous interaction of two or more substances to form a homogenous molecular dispersion.(Qualitative) • Solubility of a substance in a particular solvent is defined as the concentration of the substance in saturated solution at certain temperature. (Quantitative)
Solubility of Drugs • Solubility is an intrinsic material properties -> can be altered By chemical modification of the molecules. • Dissolution →→ is an extrinsic material property, influenced by various chemical, physical, and crystallographic means like complexations, particle size. surface properties. • Solubility of a compound depends on:  Physical, Chemical properties of the solvent and salute.  Temperature, pressure and pH of solution.
SOLUBILITY OF DRUGS Terms used in Solubility • SOLUTION It is mixture of components which are physically and chemically homogeneous. • SOLUTE The components which are present in the solution is called as solute that dissolves in solvent. • SOLVENT The medium in which components are dissolved is known as solvent. • SOLUBILITY The ability of substance to dissolve in a solvent is called solubility.
SOLUBILITY OF DRUGS Terms used in Solubility • SATURATED SOLUTION The solution containing maximum number of solute at a constant temperature is called saturated solution. • SUPER SATURATED SOLUTION A solution that contains more of the dissolved material then could be dissolved by the solvent under normal circumstances. • UNSATURATED SOLUTION A solution where the solute concentration is lower than its equilibrium solubility.
Solubility of Drugs SOLUBILITY EXPRESSION- Descriptive forms • Table-1: No. of parts of solvent requires to dissolve 1 part of the solute.
Solubility of Drugs SOLUBILITY EXPRESSION- Quantitative expression • PERCENTAGE TERM USED IN SOLUBILITY 1. % W/W = Percent Weight by Weight → No. of gram of solute dissolved in 100 gram of solution. 2. % V/V = Percent volume by volume → No. of gram of solute dissolved in 100 gram of solution. 3. % W/V = Percent Weight by volume → No. of gram of solute dissolved in 100 ml of solution.
Solubility of Drugs MOLARITY • It is defined as the number of moles (or gram molecular weight) of solute dissolved in 1 litre of solution. MOLALITY • It is defined as the moles of solute dissolved in 1000 g of solvent. NORMALITY • It is defined as the number of gram or mole equivalents of solute present in one litre of a solution. MOLE FRACTION • Mole fraction is the number of moles of a specific component in the solution divided by the total number of moles in the given solution.
Solvent-Solute Interactions • Binding forces between molecules Cohesive and adhesive forces are manifestation of intermolecular force. • When molecule interact both repulsion force and attraction forces act. • To cohere attraction forces are necessary and to prevent interpenetration repulsion forces are required.
Solvent-Solute Interactions  Types of attraction forces • Van der Waals Force  Dipole-dipole interaction (Keesom interactions)  Dipole-induced dipole interaction (Debye interactions)  Induced-dipole -Induced-dipole interaction (London dispersion forces) • Ion-Dipole and ion-Induced Dipole Force • Ion-ion Interaction • Hydrogen Bonds  Selection of solvent is based on 'like dissolve like’
Solvent Solutes Interactions • Water is good solvent for –salt and Sugar& similar compounds • Mineral oils dissolve - normally only slightly water soluble substances • So “like dissolves like”
Solvent Solutes Interactions Polar Solvents- • Solubility of drug is due to polarity of solvent that is dipole moment. • Polar solvents dissolves ionic solutes Polar substances • Water mixes in all proportions with  Alcohol  Sugars  Other polyhydroxy compounds.
Solvent Solutes Interactions • Hildebrand showed that a consideration of dipole moments, alone is not adequate to explain solubility of, polar substances in water • The ability of the solute to form hydrogen bonds is more significant factor. • Water dissolves → phenols, alcohols. aldehydes, ketones, amines, and other. oxygen and nitrogen containing compounds that can form hydrogen bonds. with water. • Difference in acid- base character of constituents (in the Lewis electron donor-acceptor sense) also contributes to specific interaction in solutions.
Solvent Solutes Interactions Nonpolar solvents • Nonpolar solvents unable to reduce attraction b/w ions of strong and weak electrolytes because solvent low dielectric constants. • Non polar solvent dissolve non polar solute with similar internal pressure.
Solvent Solutes Interactions Nonpolar solvents • The solute molecules are kept in solution by weak van der Waals, London types of forces. • Oil and fats dissolved in carbon tetrachloride benzene and mineral oils. • Alkaloids bases and fatty acids dissolves in non polar solvents.
Solvent Solutes Interactions Semipolar Solvents- • Semipolar solvents → ketones and alcohols. induce certain degree of polarity in non polar solvents. • Example-benzene (readily polarizable) become soluble in alcohol. • Semipolar compounds can act as intermediate solvents - bring miscibility of polar and nonpolar liquids.
Mechanism of Solute-Solvent Interaction • If the solvent is A & the solute is B. and the forces of attraction are represented by A-A, B- B and A-B. • If A-A >> A-B The solvent molecules will be attracted to each other. • Example: Benzene & water, where benzene molecules are unable to penetrate the closely bound water aggregates.
Mechanism of Solute-Solvent Interaction • If B-B >> A-A The solvent will not be able to break the binding forces between solute molecules. • Example NaCl in benzene, where the NaCl crystal is held by strong electrovalent forces which cannot be broken by benzene. • If A-B >> A-A or B-B, or the three forces are equal. Formation of solution takes place. • Example: NaCl in water. • Solution is formed when Solvent-solvent interaction < Solvent -solute interaction > Solute -solute interaction.
Any query?
Thank you.