**Question 12:**Which of the following carbocations is the least stable one?- A diagram with four different carbocations is shown. Each carbocation is depicted with a positive charge (+) symbol. They are based on different alkyl groups or structures supporting the carbocation.**Question 13:**The heats of complete hydrogenation of the following three hydrocarbons are 105, 116, 275, and 292 (in kJ/mol). Which hydrocarbon does feature the heat of hydrogenation of 292 kJ/mol?- A diagram with four different hydrocarbon structures is shown, which include alkenes and an alkyne. Each structure has differing levels of unsaturation.**Explanation of Diagrams:**In Question 12, each of the carbocations is in a different molecular environment. The stability of the carbocation is influenced by factors such as resonance, hyperconjugation, and the nature of the carbon atom holding the positive charge.In Question 13, each hydrocarbon has a different degree of saturation. The heat of hydrogenation is indicative of the stability of the hydrocarbon, with higher values typically corresponding to less stable structures. Alkenes and alkynes are depicted with different numbers and arrangements of double and triple bonds.

Carbocation is a carbon that form 3 covalent bonds and carries a positive charge as it has an empty p-orbital. Hence, carbocation is an electron deficient species. The given carbocation are as follows: 1. Secondary carbocation: carbocation that forms two bond with carbon atoms and 1 with hydrogen. 2. Vinyl carbocation: carbocation on double bonded carbon. 3. Tertiary carbocation : carbocation that forms 3 bonds with carbon atoms. Secondary and tertiary carbocation are alkyl carbocation and vinyl carbocation is alkenyl carbocation. Carbocation are electron deficient species. It requires electron density for its stability. Tertiary carbocation has three alkyl groups that increases electron density on carbon containing positive charge making it stable by +I effect (Inductive effect). While secondary carbocation has two alkyl groups therefore only 2 alkyl groups will stabilize the carbocation. Therefore, tertiary carbocation is more stable than secondary carbocation. Alkyl carbocation is more stable than vinyl carbocations. More the s character more is the electronegativity. Alkyl carbocation have positive charge on sp2 hybridized carbon atom. s character is 33.3% Vinyl carbocation have positive charge on sp hybridized carbon atom. s character is 50% Carbon of vinyl carbocation is more electronegative than in alkyl carbocation due to higher s character. Due to greater electronegativity, the carbon of vinyl carbocation destabilizes the positive charge of carbocation by pulling the electron density of carbocation. Hence, the vinyl carbocation is least stable. Answer: 2. Vinyl carbocation is least stable.