Estimate the heat of formation of gaseous isoprene
$(H_{2} C = C H_{3} | c - H | C = C H_{2})$ from the following data;
Bond energies:
$C - H$ = 98.8 kcal/mole
$H - H$ = 104.0 kcal/mole
$C - C$ = 83.1 kcal/mole
$C = C$ = 147.0 kcal/moleHeat of sublimation of carbon (s) = 171.7 kcal per mole

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Solution

Isoperene is $H_{2} C = C H_{3} | C - H | C = C H_{2}$

$5 C (g r a p h i t e) + 4 H_{2} (g) \to H_{2} C = C H_{3} | C - H | C = C H_{2}$

$Δ H = 5 Δ H_{s u b . C} + 4 B . E_{H - H} - (8. B . E_{C - H} + 2 B . E_{C = C} + 2 B . E_{C - C})$

$Δ H = 5 \times 171.7 + 4 \times 104.0 - (8 \times 98.8 + 2 \times 147.0 + 2 \times 83.1)$

$Δ H = 1274.5 - (1250.6) = + 23.9 K c a l$

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The bond dissociation energy of H-H, C-C,C-H bonds respectively are 104.2, 83.1 and 98.8kcal/mole . The electronegative of c is?

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X_{H} = 2.1.

The bond dissociation energy of H - H, C - C, and C - H bonds respectively are 104.2, 83.1 and 98.8 kcal/ mole. The electronegativity of C is?

The bond dissociation energy of H - H, C - C, and C - H bonds respectively are 104.2, 83.1 and 98.8 Kcal/ mole. The electro negativity of e is

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128.5 x \times 10^{- 2}

x

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