Organic chemistry/Alcohols

In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a saturated carbon atom, The term alcohol originally referred to the primary alcohol ethanol (ethyl alcohol), which is used as a drug and is the main alcohol present in alcoholic drinks. An important class of alcohols, of which methanol and ethanol are the simplest members, includes all compounds for which the general formula is CnH2n+1OH. Simple mono-alcohols that are the subject of this article include primary (RCH2OH), secondary (R2CHOH) and tertiary (R3COH) alcohols.

Naming

The suffix -ol appears in the IUPAC chemical name of all substances where the hydroxyl group is the functional group with the highest priority. When a higher priority group is present in the compound, the prefix hydroxy- is used in its IUPAC name. The suffix -ol in non-IUPAC names (such as paracetamol or cholesterol) also typically indicates that the substance is an alcohol. However, many substances that contain hydroxyl functional groups (particularly sugars, such as glucose and sucrose) have names which include neither the suffix -ol, nor the prefix hydroxy-

Informal/Common names

In less formal contexts, an alcohol is often called with the name of the corresponding alkyl group followed by the word "alcohol", e.g., methyl alcohol, ethyl alcohol.

Alcohols are then classified into primary, secondary (sec-, s-), and tertiary (tert-, t-), based upon the number of carbon atoms connected to the carbon atom that bears the hydroxyl functional group. (The respective numeric shorthands 1°, 2°, and 3° are also sometimes used in informal settings).

Type	Formula	IUPAC Name	Common name
Monohydric alcohols	CH3OH	Methanol	Wood alcohol
	C2H5OH	Ethanol	Alcohol
	C3H7OH	Propan-2-ol	Isopropyl alcohol, Rubbing alcohol
	C4H9OH	Butan-1-ol	Butanol, Butyl alcohol
	C5H11OH	Pentan-1-ol	Pentanol, Amyl alcohol
	C16H33OH	Hexadecan-1-ol	Cetyl alcohol
Polyhydric alcohols	C2H4(OH)2	Ethane-1,2-diol	Ethylene glycol
	C3H6(OH)2	Propane-1,2-diol	Propylene glycol
	C3H5(OH)3	Propane-1,2,3-triol	Glycerol
	C4H6(OH)4	Butane-1,2,3,4-tetraol	Erythritol, Threitol
	C5H7(OH)5	Pentane-1,2,3,4,5-pentol	Xylitol
	C6H8(OH)6	hexane-1,2,3,4,5,6-hexol	Mannitol, Sorbitol
	C7H9(OH)7	Heptane-1,2,3,4,5,6,7-heptol	Volemitol
Unsaturated aliphatic alcohols	C3H5OH	Prop-2-ene-1-ol	Allyl alcohol
	C10H17OH	3,7-Dimethylocta-2,6-dien-1-ol	Geraniol
	C3H3OH	Prop-2-yn-1-ol	Propargyl alcohol
Alicyclic alcohols	C6H6(OH)6	Cyclohexane-1,2,3,4,5,6-hexol	Inositol
	C10H19OH	5-Methyl-2-(propan-2-yl)cyclohexan-1-ol	Menthol

Formal settings

IUPAC nomenclature is used in scientific publications and where precise identification of the substance is important, especially in cases where the relative complexity of the molecule does not make such a systematic name unwieldy. In naming simple alcohols, the name of the alkane chain loses the terminal e and adds the suffix -ol, e.g., as in "ethanol" from the alkane chain name "ethane". When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the -ol: propan-1-ol for CH
₃CH
₂CH
₂OH, propan-2-ol for CH
₃CH(OH)CH
₃. If a higher priority group is present (such as an aldehyde, ketone, or carboxylic acid), then the prefix hydroxy-is used, e.g., as in 1-hydroxy-2-propanone (CH
₃C(O)CH
₂OH).

Some examples of simple alcohols and how to name them

CH3–CH2–CH2–OH
n-propyl alcohol, propan-1-ol, or 1-propanol	isopropyl alcohol, propan-2-ol, or 2-propanol	cyclohexanol	isobutyl alcohol, 2-methylpropan-1-ol, or 2-methyl-1-propanol	tert-amyl alcohol, 2-methylbutan-2-ol, or 2-methyl-2-butanol
A primary alcohol	A secondary alcohol	A secondary alcohol	A primary alcohol	A tertiary alcohol