Answer to Question #194659 in Organic Chemistry for Joshua

Question

Explain the following; (4 marks)

i. The H’s in ethyne are considerably more acidic than those in ethane (Illustrate your point with 

chemical equations). 

ii. A cycloheptene (very unstable thougth) can be made but cycloheptyne has never been made.

Answer 1

In ethyne the C atoms are sp hybridised with 50 %of s character. As the s character increases the electronegativity increases. In this way the carbon atom in ethyne attracts the electron pair of C -H bond towards itself and H+ ions are set free. Hence ethyne acts as an acid as it can easily donate H+ ions. In comparison to this carbon atom in ethane is sp3 hybridised with 25%s character which is less electronegative so it is difficult for it to easily donate H +ions.