Pent-1-ene, CH2=CHCH2CH2CH3\text{CH}_2\text{=CHCH}_2\text{CH}_2\text{CH}_3CH2=CHCH2CH2CH3, and penta-1,4-diene, CH2=CHCH2CH=CH2\text{CH}_2\text{=CHCH}_2\text{CH=CH}_2CH2=CHCH2CH=CH2, are unsaturated hydrocarbons.
Explain what is meant by the terms σ\sigmaσ-bond and π\piπ-bond.
State the number of σ\sigmaσ-bonds and π\piπ-bonds present in one molecule of penta-1,4-diene, CH2=CHCH2CH=CH2\text{CH}_2\text{=CHCH}_2\text{CH=CH}_2CH2=CHCH2CH=CH2.
Pent-1-ene reacts with hydrogen chloride, HCl\text{HCl}HCl, via electrophilic addition to form two structural isomers, one of which is formed in a much greater quantity (the major product).
Describe the stepwise mechanism for the formation of the major product, including the formulas of the intermediate species and the final product.
Explain, in terms of carbocation stability, why this major product is formed in preference to the minor product.
