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Chapter 26: Q13P (page 1334)

(a) Nomex®, a strong fire-resistant fabric, is a polyamide made from meta-phthalic acid and meta-diaminobenzene. Draw the structure of Nomex.

(b) Kevlar®, made from terephthalic acid (para-phthalic acid) and para-diaminobenzene, is used in making tire cord and bulletproof vests. Draw the structure of Kevlar.

Short Answer

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a)

b)

Step by step solution

01

Introduction

Nomex® and Kevlar ® are Aramids or aromatic polyamide, a family of nylons. Their blends are used to make fireproof clothing. They are heat-resistant and have strong synthetic fibers.

02

(a) Nomex

Nomex® has meta-phenylene groups, in which the amide groups are attached to the phenyl ring at the 1 and 3 positions.

03

(b) Kelvar

Kevlar ® is a polyamide, in which all the amide groups are separated by para-phenylene groups, which means, the amide groups attach to the phenyl rings opposite to each other, at carbons 1 and 4.

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Most popular questions from this chapter

(a) Propose a mechanism for the reaction of bisphenol A with phosgene.

(b) Diethyl carbonate serves as a less-toxic alternative to phosgene for making Lexan. Propose a mechanism for the transesterification of diethyl carbonate with bisphenol A, catalyzed by a trace of sodium ethoxide. What small molecule is given off in this condensation?

Chain branching occurs in cationic polymerization much as it does in free-radical polymerization. Propose a mechanism to show how branching occurs in the cationic polymerization of styrene. Suggest why isobutylene might be a better monomer for cationic polymerization than styrene.

Explain why the addition of a small amount of glycerol to the polymerization mixture gives a stiffer urethane foam.

Bisphenol A is made on a large scale by a condensation of phenol with acetone. Suggest an appropriate catalyst, and propose a mechanism for this reaction. (Hint: This is a condensation because three molecules are joined with loss of water. The mechanism belongs to another class of reactions though.)

In reference to cloth or fiber, the term acetate usually means cellulose acetate, a semisynthetic polymer made by treating cellulose with acetic anhydride. Cellulose acetate is spun into yarn by dissolving it in acetone or methylene chloride and forcing the solution through spinnerets into warm air, where the solvent evaporates.

(a) Draw the structure of cellulose acetate.

(b) Explain why cellulose acetate is soluble in organic solvents, even though cellulose is not.

(c) (A true story) An organic chemistry student wore a long-sleeved blouse to the laboratory. She was rinsing a warm separatory funnel with acetone when the pressure rose and blew out the stopper. Her right arm was drenched with acetone, but she was unconcerned because acetone is not very toxic. About ten minutes later, the right arm of the student’s blouse disintegrated into a pile of white fluff, leaving her with a ragged short sleeve and the tatters of a cuff remaining around her wrist. Explain how a substance as innocuous as acetone ruined the student’s blouse.

(d) Predict what usually happens when students wear polyvinyl chloride shoes to the organic laboratory.
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