Chemistry, Third edition

ALCOHOLS

Physical properties of alcohols

1. Ability to hydrogen bond

The–OH group in an alcohol is polar:

R—O

—

H



Alcohols are therefore able to hydrogen bondwith themselves or with water:

331

Table 18.2Some members of the alcohol family

Name Formula Boiling point/°C State at
room temparature

Methanol CH 3 OH 165 l
Ethanol CH 3 CH 2 OH 179 l

Higher alcohol members can exist in isomeric forms – notice how they are named
Propan-1-ol CH 3 CH 2 CH 2 OH 198 l
Propan-2-ol CH 3 CHOHCH 3 183 l
Butan-1-ol CH 3 CH 2 CH 2 CH 2 OH 117 l
CH 3
|
2-Methylpropan-2-ol CH 3 COHCH 3 182 s/l

Example 18.1

Name the compound: OH OH

||

CH 2 CH 2

Answer

ethane-1,2-diol (old name ethylene glycol)

Nomenclature of alcohols

(i)Name and write the structural formulae for the different isomers of pentanol, C 5 H 11 OH.

There are eight.

(ii)Glycerol, or propane-1,2,3-triol, is used in many cosmetic preparations to make them feel

soft. Write its structural formula.

Exercise 18B