(a) (i) Draw the structures of the isomers of the alkene with molecular formurat C\(_4\)H\(_8\)
(ii) State the class of alkanols to which each of the following compounds belongs:
I. CH\(_3\)C(CH\(_3\))\(_2\)OH;
II. CH\(_3\)CH(CH\(_3\))CH\(_2\)OH;
III. CH\(_3\)CH\(_2\)CH(CH\(_3\))OH.
(b) (i) Write the formulae of the products formed in the following reactions:
I. CH\(_3\)CH\(_2\)COOH \(\frac{K_{(s)}}{}\)
II. CH\(_3\)CH\(_2\)COOH. \(\frac{C_4H_6OH, heat}{Conc.H_2SO_4}\)
III. CH\(_3\)CH\(_2\)CH\(_2\)CH\(_2\)OH \(\frac{H^+/KMnO_4}{(excess)}\)
(ii) Name the major product(s) of each of the reactions in (b)(i).
(c) A gaseous hydrocarbon R of mass 7.0 g occupies a volume of 2.24 dm\(^3\) at s. t.p. If the percentage composition by mass of hydrogen is 14.3, determine its:
(i) empirical formula;
(ii) molecular formula. [ H = 1.00, C = 12.0, Molar volume of gas at s.t.p, = 22.4 dm\(^3\) ]
(d) Define structural isomerism.
Explanation
(a)(i) Structural Isomers of C\(_4\)H\(_4\)
(ii) (I)Tertiary(3°)alkanol.
(II) Primary (1°)alkanol.
(III) Secondary (2°) alkanol
(b)(i)
(I) CH\(_3\)CH\(_2\)COOK, H\(_2\)
(II) CH\(_3\)CH\(_2\)COOC\(_4\)H\(_9\) H\(_2\)O
(III) CH\(_3\)CH\(_2\)CH\(_2\)COOH
(ii) Major products in (b)(i) (1) — Potassuim propanoate (II) — Butyl propanoate (III) — Butanoic acid
(C)(i) % carbon by mass = 100 – 14.3 (l) = 85.7%
Ratio of atoms = \(\frac{C}{\frac{85.7}{12.0}}\) = 7.1415; \(\frac{H}{\frac{14.3}{1.0}}\) = 14.3
Divide by smaller number = \(\frac{7.1415}{7.1415}\) = 1; \(\frac{14.3015}{7.1415}\) = 2
Empirical Formular = CH\(_2\)
(i) 2.24dm\(^3\) = 7.0g of R
22.4dm\(^3\) = \(\frac{7.0}{2.24}\) x 22.4 = 70gmol\(^1\)
OR
Molar volume of gas = 22.4 dm\(^3\) at s.t.p 22.4
22.4 dm\(^3\) gas = 1 mole
22.4 dm\(^3\) = \(\frac{2.24}{22.4} \times 1\) = 0.1 mol
But numbers of moles = 0.1
Mr = \(\frac{7}{0.1}\) = 70gmol\(^1\)
Molecular formular = C\(_5\)H\(_{10}\)
(CH_2)n = 70
14n = 70
n = \(\frac{70}{4}\) = 5
(d) The occurence of / existence of / condition whereby compounds with the same molecular formula have different structural formulae.