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.

NamingEdit

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 namesEdit

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 settingsEdit

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".[1] 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
3
CH
2
CH
2
OH
, propan-2-ol for CH
3
CH(OH)CH
3
. If a higher priority group is present (such as an aldehyde, ketone, or carboxylic acid), then the prefix hydroxy-is used,[1] e.g., as in 1-hydroxy-2-propanone (CH
3
C(O)CH
2
OH
).[2]

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
  1. 1.0 1.1 William Reusch. "Alcohols". VirtualText of Organic Chemistry. Archived from the original on 19 September 2007. Retrieved 14 September 2007.
  2. Organic chemistry IUPAC nomenclature. Alcohols Rule C-201.