Integrated SequencePhysics Chemistry Organic Biology

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Module 7 in the Syllabus

Physical Properties of Organic Compounds Images
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Question Drill for The Physical Properties of Organic Compounds
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Overview of The Physical Properties of Organic Compounds
In addition to reactivity, the physical properties of an organic substance, such as melting point, boiling point and solubility, are amont its most important traits. The physical properties of an organic substance can often be predicted from its structure. In most cases, a substance's molecular weight and the functional groups are sufficient information to allow for a good estimate of the melting point, boiling point, and solubility to be estimated. Comparing molecules of similar size, the greater the strength of intermolecular force, the more equilibrium will favor the condensed phase at a given pressure and temperature.

The Physical Properties of Organic Compounds on the MCAT
Understanding how functional groups affect the physical properties of organic compounds is of primary importance to laboratory organic chemistry, and, furthermore, one of the bridges from organic chemistry to biochemistry and cell biology. The student must obtain this form of understanding to be able to grasp protein folding, for example, or the structure of biological membranes. Every MCAT makes this area a priority. You can expect both direct and indirect questions. Straightforward questions asking for a comparison of solubilities are common, for example, as are questions involving similar reasoning in a more advanced biological context.

Conceptual Vocabulary
HydrophobicityHydrophobicity refers to the physical property of a molecule that is repelled from a mass of water
HydrocarbonA hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.
HydrophilicityHydrophilicity refers to a physical property of a molecule that can transiently bond with water through hydrogen bonding.
MiscibilityMiscibility is a term in chemistry that refers to the property of liquids to mix, forming a homogeneous solution.
LipophilicityLipophilicity refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene.
Aliphatic compoundAliphatic compounds are organic compounds in which carbon atoms are joined together in straight or branched chains or in rings, that can be either saturated or unsaturated, but not aromatic.
ParaffinParaffin is a common name for the group of alkane hydrocarbons.
VolatilityVolatility is a measure of the speed at which a substance turns into a vapor from a solid or liquid state.
Volatile organic compoundVolatile organic compounds (VOCs) are organic chemical compounds that have high enough vapour pressures under normal conditions to significantly vaporize and enter the atmosphere.
AmphiphileAmphiphile is a term describing a chemical compound possessing both hydrophilic and hydrophobic properties.
Partition coefficientA partition or distribution coefficient is the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium.
Protic solventA protic solvent is a solvent that carries a hydrogen bond between an oxygen as in a hydroxyl group or a nitrogen as in an amine group.
Liquid-liquid extractionLiquid-liquid or solvent extraction, also known as partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent.
HygroscopyHygroscopy is the ability of a substance to attract water molecules from the surrounding environment through either absorption or adsorption.
Multiphasic liquidA multiphasic liquid is a mixture consisting of more than two immiscible liquid phases.
Relative volatilityRelative volatility is a measure of the vapor pressure differences of the components in a liquid mixture of chemicals.
Advanced terms that may appear in context in MCAT passages
BolaamphiphileBolaamphiphiles are amphiphilic molecules that have hydrophilic groups at both ends of a sufficiently long hydrophobic hydrocarbon chain.
LipophobicityLipophobicity is a term which literally means fat rejection and describes compounds which are not soluble in lipids or other non-polar solvents.
Flory-Huggins solution theoryFlory-Huggins solution theory is a mathematical model of the thermodynamics of polymer solutions which takes account of the great dissimilarity in molecular sizes in adapting the usual expression for the entropy of mixing.
LyotropicA material is called lyotropic if it forms liquid crystal phases because of the addition of a solvent.

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