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Chapter 26: Q23P (page 1342)

. Poly (trimethylene carbamate) is used in high-quality synthetic leather. It has the structure shown.

(a) What type of polymer is poly (trimethylene carbamate)?

(b) Is this a chain-growth polymer or a step-growth polymer?

(c) Draw the products that would be formed if the polymer were completely hydrolyzed under acidic or basic conditions.

Short Answer

Expert verified

(a)It is a polyurethane.

(b) As with all polyurethanes, it is a step-growth polymer.


Step by step solution

01

Step-1. Explanation of part (a) and (b):

Poly (trimethylene carbamate) is a polyurethane. Polyurethanes refers to class of polymers which are composed of organic units joined by carbamate links. These are family of plastics, and they are durable, flexible and adaptable.

Poly (trimethylene carbamate) is a step-growth polymer and undergoes step-growth polymerisation in which formation of polymer occurs from bi-functional or multifunctional monomers.

02

Step-2. Explanation of part (c):

Poly (trimethylene carbamate) if completely hydrolysed under acidic or basic conditions, then it would result in the formation of amino alcohol and also carbon-dioxide will get released in this process. Cleavage of nitrogen-carbon bond occurs which gives rise to intermediates and these intermediates rearrange to form amino alcohol and carbon dioxide gas as release of gas increases entropy of the system, thus this process is favourable.

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Most popular questions from this chapter


Cholic acid, a major constituent of bile, has the structure shown.

(a) Draw the structure of cholic acid, showing the rings in their chair conformations, and label each methyl group and hydroxy group as axial or equatorial. (Making a model may be helpful.)

(b) Cholic acid is secreted in bile as an amide linked to the amino group of glycine. This cholic acid-amino acid combination acts as an emulsifying agent to disperse lipids in the intestines for easier digestion. Draw the structure of the cholic acid-glycine combination and explain why it is a good emulsifying agent.

(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.

Plywood and particle board are often glued with cheap, waterproof urea-formaldehyde resins. Two to three moles of formaldehyde are mixed with one mole of urea and a little ammonia as a basic catalyst. The reaction is allowed to proceed until the mixture becomes syrupy, and then it is applied to the wood surface. The wood surfaces are held together under heat and pressure, while polymerization continues and cross-linking takes place. Propose a mechanism for the base-catalyzed condensation of urea with formaldehyde to give a linear polymer, and then show how further condensation leads to cross-linking. (Hint: The carbonyl group lends acidity to the N - Hprotons of urea. A first condensation with formaldehyde leads to an imine, which is weakly electrophilic and reacts with another deprotonated urea.)

Poly (vinyl alcohol), a hydrophilic polymer used in aqueous adhesives, is made by polymerizing vinyl acetate and then hydrolyzing the ester linkages.

(a) Give the structures of poly (vinyl acetate) and poly (vinyl alcohol).

(b) Vinyl acetate is an ester. Is poly (vinyl acetate) therefore a polyester? Explain.

(c) We have seen that basic hydrolysis destroys the Dacron polymer. Poly (vinyl acetate) is converted to poly (vinyl alcohol) by a basic hydrolysis of the ester groups. Why doesn’t the hydrolysis destroy the poly (vinyl alcohol) polymer?

(d) Why is poly (vinyl alcohol) made by this circuitous route? Why not just polymerize vinyl alcohol?
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