Page 287 - Theory and Problems of BEGINNING CHEMISTRY

276 ORGANIC CHEMISTRY [CHAP. 18

18.24. Identify the radical(s) and the functional group in each of the following molecules: (a)CH 3 OH,
(b)CH 3 CO 2 H, (c)CH 3 CHO, and (d)CH 3 CH 2 OCH 3 .
Ans. Radical(s) Functional Group

(a)CH 3 − −OH
(b)CH 3 − −CO 2 H
(c)CH 3 − −CHO
(d)CH 3 CH 2 − and −CH 3 −O−

ALCOHOLS
18.25. Explain why an alcohol, ROH, is not a base.
Ans. The OH group is not ionic.

18.26. Write the formula of another alcohol isomeric with CH 3 CH 2 CH 2 OH.
Ans. CH 3 CHOHCH 3 (The −OH group can be attached to the middle carbon atom.)

ETHERS
18.27. Write line formulas for (a) dipropyl ether, (b) ethyl phenyl ether, and (c) methyl butyl ether.
Ans. (a)CH 3 CH 2 CH 2 OCH 2 CH 2 CH 3 (b)CH 3 CH 2 OC 6 H 5 (c)CH 3 OCH 2 CH 2 CH 2 CH 3

18.28. Write the line formula for an ether that is an isomer of (a)CH 3 CH 2 OH and (b)CH 3 CH 2 CH 2 OH.
Ans. (a)CH 3 OCH 3 (b)CH 3 CH 2 OCH 3

18.29. Write the formulas of all alcohols isomeric with CH 3 CH 2 OCH 2 CH 3 .

Ans. CH 3 CH 2 CH 2 CH 2 OH and CH 3 CH 2 CHOHCH 3 , (CH 3 ) 2 CHCH 2 OH, and (CH 3 ) 2 COHCH 3 .

ALDEHYDES AND KETONES
18.30. Explain why the simplest ketone has three carbon atoms.
Ans. A ketone has a doubly bonded oxygen atom on a carbon that is not an end carbon atom. The smallest carbon
chain that has a carbon not on an end has three carbon atoms.
18.31. Write balanced chemical equations for the catalytic reduction by hydrogen gas to the corresponding
alcohol for (a)CH 3 CH 2 CHO and (b)CH 3 COCH 3 .
catalyst
Ans. (a)CH 3 CH 2 CHO + H 2 −−→ CH 3 CH 2 CH 2 OH
catalyst
(b)CH 3 COCH 3 + H 2 −−→ CH 3 CHOHCH 3
In each case, the hydrogen molecule adds across the C O double bond.

ACIDS AND ESTERS
18.32. Contrast the following two formulas for acetic acid: HC 2 H 3 O 2 and CH 3 CO 2 H. Explain the advantages
of each. Which hydrogen atom is lost upon ionization of acetic acid in water?
Ans. The first formula is easily identified as an acid, with H written first. It is that hydrogen atom which ionizes
in water. The second formula shows the bonding. The hydrogen atom attached to the oxygen atom ionizes
in water.