To determine how many alkenes produce 2,3-dimethyl-2-butanol upon acid hydration, we need to understand the hydration reaction and the structure of the alcohol.

Step 1: Understand Acid Hydration of Alkenes
Acid hydration of alkenes follows Markovnikov's rule. Water adds across the double bond, with the hydrogen attaching to the less substituted carbon and the hydroxyl group attaching to the more substituted carbon. The general reaction is: $R - CH = CH - R^{'} + H_{2} O \overset{H^{+}}{\to} R - CH (OH) - CH 2 - R^{'}$

Step 2: Analyze the Product Alcohol
The product is 2,3-dimethyl-2-butanol. Its structure is: ${(CH)_{3}}_{3} C - C H (CH)_{3}) - C H_{3} or {(CH)_{3}}_{3} C - C (OH) (CH)_{3}) - C H_{3}$ This is a tertiary alcohol because the carbon with the OH group is attached to three alkyl groups.

Step 3: Determine Possible Alkene Precursors
Since hydration gives a tertiary alcohol, the alkene must have the double bond such that the more substituted carbon (which gets the OH) is tertiary. For 2,3-dimethyl-2-butanol, the carbon with OH is carbon 2, which is bonded to two methyl groups and one ethyl-like group (CH(CH3)CH3), but actually it is a tertiary carbon with three carbons: two methyl and one ethyl. So, the possible alkenes are those that upon Markovnikov addition yield this structure.

The possible alkenes are:

2,3-Dimethyl-2-butene: ${(CH)_{3}}_{3} C = C (CH)_{3}) - C H_{3}$ Hydration gives the tertiary alcohol directly.
2,3-Dimethyl-1-butene: $H_{2} C = C (CH)_{3}) - C H_{3} (CH)_{3})$ Markovnikov addition puts OH on the tertiary carbon (carbon 2), giving the product.
3,3-Dimethyl-1-butene: $H_{2} C = C H - C (CH)_{3})_{3}$ Hydration gives (CH3)3C-CH2-CH2OH, which is not the desired alcohol.
Other isomers: We must consider all alkenes with formula C6H12 that can hydrate to C6H14O. The alcohol has formula C6H14O. The alkenes are C6H12. After checking all structural isomers with a double bond that can yield a tertiary alcohol with this carbon skeleton, we find that only two alkenes give exactly 2,3-dimethyl-2-butanol: 2,3-dimethyl-2-butene and 2,3-dimethyl-1-butene. 3,3-dimethyl-1-butene gives a primary alcohol. Other isomers like 3-methyl-2-pentene might give different alcohols.

Upon detailed analysis, there are exactly 2 alkenes that produce 2,3-dimethyl-2-butanol upon acid hydration: 2,3-dimethyl-2-butene and 2,3-dimethyl-1-butene.

Final Answer: 2

Related Topics

Markovnikov's Rule: In the addition of HX to an unsymmetrical alkene, the hydrogen atom attaches to the carbon with more hydrogen atoms, and the halogen (or OH in hydration) attaches to the carbon with fewer hydrogen atoms (more substituted carbon).

Tertiary Alcohols: Alcohols where the carbon bearing the OH group is attached to three alkyl groups. They are formed from alkenes where the double bond is such that one carbon is tertiary.

Formulae

General hydration reaction: $R - CH = CH - R^{'} + H_{2} O \overset{H^{+}}{\to} R - CH (OH) - CH 2 - R^{'}$