MCAT Organic Chemistry > Alcohols

Background

About the MCAT - Organic Chemistry - Alcohols - Alcohol Image

An alcohol is any oxygen containing organic compound with the general formula R-OH.

Alcohol Nomenclature

Alcohols are either given the prefix hydroxyl or hydroxy.

Alcohols are named in the IUPAC system by replacing the –e ending of the root alkane with the ending –ol. The carbon atom attached to the hydroxyl group must be included in the longest chain and receives the lowest possible number.

MCAT Alcohols - Alcohol Nomenclature

Alternatively, the alkyl group can be named as a derivative, followed by the word alcohol, e.g. ethyl alcohol, isobutyl alcohol.

Alcohol Properties

MCAT Alchols - Alcohol Physical Properties

Boiling points of alcohols are significantly higher than those of structurally isomeric hydrocarbons due to hydrogen bonding.

Molecules with more than one hydroxyl (-OH) group show increased levels of hydrogen bonding.

Learn the pKas of alcohols. Phenyl alcohols, or phenols, are more acidic than normal alcohols.

Alcohols are usually water soluble if they are not attached to a hydrophobic molecule.

Hydrogen bonding is the main reason alcohols tend to have higher boiling points analogous organic compounds.

The table below compares the acidity of alcohols with other groups of oxygen-containing compounds.

A lower pka denotes a higher acidity to the compound.

CompoundExamplepKa
COOHCarboxylic Acids5
Ar-OHPhenols10
H2OWater16
R-OHAlcohols15
-CH2(CO)-RAldehydes and Ketones20
-CH2(CO)-ORKeto Acids and Esters25

Additional branching on an alcohol will decrease the melting point and boiling point.

The infrared spectroscopy of the OH group occurs around 3300 cm-1 due to the high energy hydrogen bond.

Alcohol Reactions

See Alcohol Reactions

MCAT Organic Chemistry

Organic Chemistry Topics