Write the structural formula of: (i) 2,2,4-trimethylpentane

 Write the structural formula of: (i) 2,2,4-trimethylpentane (ii) ethylmethanoate (iii) trans 2,3-dimethylbut-2-ene (b) Write the structure of the straight-chain compound that is isometric with 2,2,4-trimethylpentane. (c) Write chemical equations to illustrate the oxidation of (i) a secondary alkanol (ii) a dihydric alkanol (d) When crushed cassava was warned with dilute hydrochloric acid, a sweet-tasting compound, D was obtained. When compound D was treated  with the enzyme, zymase and the mixture distilled, a clear and colourless liquid, E was obtained. When liquid E was warmed with ethanoic acid in the presence of a few drops of concentrated tetraoxosulphate (VI) acid, a compound, F, with fruity smell was obtained. (i) To what class of compounds does D belong? (ii) Name E and F. (iii) Write the functional group in F. (iv) Write the equation for the reaction between E and ethanoic acid in the presence of concentrated tetraoxosulphate (VI) acid. (v) Name the type of reaction that takes place between E and ethanoic acid. (e) Arrange the following compounds in their correct order of increasing boiling points: CH3CH2CH2OH, CH3CH2CH2CH2CH2CH2CH3 and CH3CH2CH2CH3. Explain the order. 

Solution:

(i) (CH3)3CCH2CH(CH3)2

(ii) CH3COOCH3

(iii) HCH3C=CCH3H

(iv)         CH3

      CH3-C-CH2-CH-CH3

               CH3     CH3

(c)(i) Secondary alkanols are oxidized to alkanones. Example

                     CH3                        CH3

            CH3-C-OH + O2 ---->            = O

                     H                            CH3

(d)(i) D belongs to carbohydrates. 

(ii) E is ethanol while F is ethyl ethanoate. 

(iii) -COO- 

(iv) CH3CH2OH+CH3COOH---> CH3COOCH2CH3 + H2O

(v) The reaction in (iv) above is Esterification reaction.

(e) CH3-CH2-CH2-CH3,CH3-CH2-CH2-CH2-CH2-CH2-CH3 and CH3-CH2-CH2-OH

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                                 Order of increasing boiling point

Propanol  has the highest boiling point because of hydrogen bonding, followed by heptane because it is of higher molecular weight than butane which is the least in terms of boiling point.

QUESTION SOURCE: WAEC 1988 THEORY QUESTION 13(a)(i)(ii)(iii)(b)(c)(i)(ii)(d)(i)(ii)(iii)(iv)(v)(e)