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Special points of emphasis

Intermolecular Forces

Functional Groups in Organic Chemistry

The Physical Properties of Organic Compounds

Hydrogen bonding plays a significant role in determining the physical properties of amines, although the hydrogen bonds in amines are not as strong as the hydrogen bonding that occurs in alcohols. Amines are intermediate in boiling point between similar alkanes and alcohols. Amines with fewer than six or seven carbons are water soluble.



Work, Energy, and Power

Electricity

Intermolecular Forces

Functional Groups in Organic Chemistry

Thermochemistry

Chemical Thermodynamics and the Equilibrium State

Acids and Bases

Organic Acids and Bases

Of neutral organic molecules, amines are the strongest bases, although amines are still technically weak bases with basicity constant, Kb, between 10-3 to 10-5.

Here is an interesting discussion of the comparison of the basicity of different types of amines: Ammonia is more basic than primary amines which are themselves more basic than tertiary amines which are in turn more basic than secondary amines. Notice the irregularity of this patter.

This strange order of basicity occurs because of the combination of two effects, the stabilization of alkylammonium cation by the inductive release of negative charge by the alkyl substituents. The other effect, which tends in the opposite direction, is the ability of water to solvate and stabilize the cation through hydrogen bonding. While tertiary ammonium cations are more stabilized by induction, secondary ammonium cations are more stabilized by solvation.

How would the MCAT handle this type of material? This kind of discussion typifies content within a certain species of MCAT passage where the test-writer is not concerned that you had seen and retained this advanced material from your coursework but whether you have the overall fluency and comfort level to read the discussion with comprehension.




Functional Groups in Organic Chemistry

Acids and Bases

Organic Acids and Bases

Reactions of Carboxylic Acids and Derivatives

Proteins

Amino acids have a carboxyl group, amine group, hydrogen and a side chain bound to a central carbon (in proline, the amine group and the side chain have also formed a ring). Because the pK+ of carboxylic acids tends to be less than 7 while the pK+ of amines tends to be greater than 7, at neutral pH, the carboxyl group of an amino acid will strongly favor the base form (negatively charged carboxylate) while the amine group will tend to be in the acid form (positively charged ammonium). For this reason, the typical amino acid with a neutral side chain will exist as a zwitterion at neutral pH, the carboxylate group negatively charged and the ammonium group positively charged. A zwitterion is a chemical compound that is electrically neutral but carries formal positive and negative charges on different atoms.







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