The Foundations of Chemistry

Phenols are usually referred to by their common names. Examples are

As you might guess, cresols occur in “creosote,” a wood preservative.

Physical Properties

The hydroxyl group, XOH, is quite polar, whereas alkyl groups, R, are nonpolar. The

properties of alcohols depend on two factors: (1) the number of hydroxyl groups per mole-

cule and (2) the size of the nonpolar portion of the molecule.

The low-molecular-weight alcohols are soluble in water in all proportions (miscible).

Beginning with the four butyl alcohols, solubility in water decreases rapidly with increasing

molecular weight. This is because the nonpolar parts of such molecules are much larger

than the polar parts. Many polyhydric alcohols are very soluble in water because they

contain two or more polar XOH groups per molecule.

Table 27-8 shows that the boiling points of unbranched primary alcohols increase, and

their solubilities in water decrease, with increasing molecular weight. The boiling points

H

HH

HH

C C O H

polar

part

nonpolar

part

ROH:

CH 3

OH

OH

OH

OH

OH

hydroquinone o-cresol

CH 3

CH 3

OH

m-cresol

OH

resorcinol p-cresol

OH OH

CH 2 CH 2

1,2-ethanediol

ethylene glycol

(the major ingredient in

permanent antifreeze)

OH OH

CH 3 CH CH 2

1,2-propanediol

propylene glycol

OH OH

CH CH 2

OH

CH 2

1,2,3-propanetriol

glycerine or glycerol

(a moisturizer in cosmetics)

The o-, m-, and p- notation was
introduced in Section 27-6.

1070 CHAPTER 27: Organic Chemistry I: Formulas, Names, and Properties

TABLE 27-8 Physical Properties of Primary Alcohols

Normal Solubility in H 2 O

Name Formula bp (°C) (g/100 g at 20°C)

methanol CH 3 OH 65 miscible

ethanol CH 3 CH 2 OH 78.5 miscible

1-propanol CH 3 CH 2 CH 2 OH 97 miscible

1-butanol CH 3 CH 2 CH 2 CH 2 OH 117.7 7.9

1-pentanol CH 3 CH 2 CH 2 CH 2 CH 2 OH 137.9 2.7

1-hexanol CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 OH 155.8 0.59