Question

1. Dehydration of an alcohol X with a formula C,H,OH produces a hydrocarbon Y. When Y is treated with ozone, and the product hydrolysed, only one product Z is obtained. Identify X, Y and Z. 2. Two isomeric compounds A and B with the molecular formular C₂H₂O can be oxidized to C and D respectively. C reacts with fehling's solution to produce a red-brown precipitate E and another compound F. D has no reaction with fehling's solution, but gives a yellow crystalline product G when treated with 2,4-dinitrophenylhydrazine solution. (a) Give the names and structural formulae of compounds A, B, C, D and F (b) Name the compound E (c) Draw the structural formula of G (d) Describe what would be observed and name all the products formed when C is warmed with sodium dichromate(VI) solution acidified with dilute sulphuric acid. Write equations for the reactions taking place. (e) Describe how D is obtained industrially from crude petroleum.​

Answer 1

1. X is C3H8O (propan-2-ol), Y is C3H6 (propene), and Z is C3H6O (acetone).

2. (a) A is propanal (CH3CH2CHO), B is acetone (CH3COCH3), C is propanoic acid (CH3CH2COOH), D is acetone (CH3COCH3), and F is propanoic acid (CH3CH2COOH).

(b) The compound E is Cu2O (copper(I) oxide).

(c) The structural formula of G is C8H8N4O2.

(d) When C is warmed with sodium dichromate(VI) solution acidified with dilute sulphuric acid, C is oxidized to propanoic acid (CH3CH2COOH), and the dichromate(VI) ion (Cr2O7^2-) is reduced to chromium(III) ion (Cr^3+). The products formed are carbon dioxide (CO2), water (H2O), and chromium(III) sulfate (Cr2(SO4)3). The balanced equation for this reaction is:

CH3CH2CHO + 2[Cr2O7]2- + 8H+ → 2CH3CH2COOH + 4Cr^3+ + 7H2O

(e) D (acetone) is obtained industrially from crude petroleum by a process called steam cracking. In this process, crude petroleum is heated to a high temperature to produce a mixture of hydrocarbons. The mixture is then mixed with steam and heated again to break down the hydrocarbons into smaller molecules. Acetone is one of the products obtained from this process.