You can work as pairs (group of 2 students); don't forget to put your names on the assignment.

Please bring your answer sheet to my office until due date.
1. ( $25 \mathrm{pts}$ ) Write structural formulas for the products that form when 2 -pentene reacts with each of the following reagents:
a. $\mathrm{HI}$
b. $\mathrm{H}_{2}, \mathrm{Pt}$
c. $\mathrm{Br}_{2}$ in $\mathrm{CCl}_{4}$
d. $\mathrm{Hg}(\mathrm{OAc})_{2}$ in $\mathrm{THF}$ and $\mathrm{H}_{2} \mathrm{O}$, then $\mathrm{NaBH}_{4}, \mathrm{HO}^{-}$
e. $\mathrm{BH} 3: T H F$, then $\mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{HO}^{-}$
2. ( 30 pts) By using the same alkene, how do you synthesize the following alcohols? Give the alkene and show the mechanisms for each product formation.
3. (15 pts) Give the structure of the products that you would expect from the reaction of 2 butyne with:
a. One molar equivalent of $\mathrm{Br}_{2}$
b. One molar equivalent of $\mathrm{HBr}$
c. Two molar equivalents of $\mathrm{HBr}$
4. (30 pts) Propose a synthesis route for the following conversion. Give the appropriate reagents needed (it may include more than one step).

Question

You can work as pairs (group of 2 students); don't forget to put your names on the assignment.

Please bring your answer sheet to my office until due date.
1. ( $25 \mathrm{pts}$ ) Write structural formulas for the products that form when 2 -pentene reacts with each of the following reagents:
a. $\mathrm{HI}$
b. $\mathrm{H}_{2}, \mathrm{Pt}$
c. $\mathrm{Br}_{2}$ in $\mathrm{CCl}_{4}$
d. $\mathrm{Hg}(\mathrm{OAc})_{2}$ in $\mathrm{THF}$ and $\mathrm{H}_{2} \mathrm{O}$, then $\mathrm{NaBH}_{4}, \mathrm{HO}^{-}$
e. $\mathrm{BH} 3: T H F$, then $\mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{HO}^{-}$
2. ( 30 pts) By using the same alkene, how do you synthesize the following alcohols? Give the alkene and show the mechanisms for each product formation.
3. (15 pts) Give the structure of the products that you would expect from the reaction of 2 butyne with:
a. One molar equivalent of $\mathrm{Br}_{2}$
b. One molar equivalent of $\mathrm{HBr}$
c. Two molar equivalents of $\mathrm{HBr}$
4. (30 pts) Propose a synthesis route for the following conversion. Give the appropriate reagents needed (it may include more than one step).

Accepted Answer

∻Solution∻ ‖ 1 ⋮ **Identify the reaction with HI**: 2-pentene will undergo a hydrohalogenation reaction with $\mathrm{HI}$, where the hydrogen atom adds to one of the carbon atoms in the double bond, and the iodine adds to the other, following Markovnikov's rule. ‖ ‖ 2 ⋮ **Identify the reaction with $\mathrm{H}_{2}, \mathrm{Pt}$**: Hydrogenation of 2-pentene in the presence of a platinum catalyst will result in the addition of hydrogen atoms across the double bond, yielding pentane. ‖ ‖ 3 ⋮ **Identify the reaction with $\mathrm{Br}_{2}$ in $\mathrm{CCl}_{4}$**: The alkene will react with bromine to form a dibromide, where the bromine atoms add across the double bond in an anti-addition manner, resulting in 2,3-dibromopentane. ‖ ‖ 4 ⋮ **Identify the reaction with $\mathrm{Hg}(OAc)_{2}$ in $\mathrm{THF}$ and $\mathrm{H}_{2} \mathrm{O}$, then $\mathrm{NaBH}_{4}, \mathrm{HO}^{-}$**: This is an oxymercuration-demercuration reaction. The alkene reacts with mercuric acetate in tetrahydrofuran (THF), followed by reduction with sodium borohydride to yield an alcohol. The alcohol forms at the more substituted carbon following Markovnikov's rule. ‖ ‖ 5 ⋮ **Identify the reaction with $\mathrm{BH}_{3}: \mathrm{THF}$, then $\mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{HO}^{-}$**: This is a hydroboration-oxidation reaction. The borane adds to the less substituted carbon of the double bond in an anti-Markovnikov fashion, followed by oxidation to give the corresponding alcohol. ‖ ∻Answer∻ ⚹ a. 2-iodopentane b. Pentane c. 2,3-dibromopentane d. 2-pentanol e. 1-pentanol ⚹ ∻Key Concept∻ ⚹ Electrophilic addition reactions of alkenes ⚹ ∻Explanation∻ ⚹ Alkenes undergo addition reactions with different reagents, leading to the formation of halogenated compounds or alcohols, depending on the specific reagents and conditions used. ⚹ ∻Solution∻ ‖ 1 ⋮ **Synthesize the alcohols**: To synthesize the alcohols from 2-pentene, we need to consider reactions that will add hydroxyl groups to the molecule in a regioselective manner. ‖ ∻Answer∻ ⚹ The synthesis of specific alcohols from 2-pentene would require detailed reaction mechanisms, which are not provided in the question. ⚹ ∻Key Concept∻ ⚹ Synthesis of alcohols from alkenes ⚹ ∻Explanation∻ ⚹ Alcohols can be synthesized from alkenes through various reactions such as hydroboration-oxidation or oxymercuration-demercuration, which add hydroxyl groups to the carbon atoms of the double bond. ⚹ ∻Solution∻ ‖ 1 ⋮ **Reaction of 2-butyne with $\mathrm{Br}_{2}$**: One molar equivalent of bromine will add across the triple bond of 2-butyne to form a dibromoalkene. ‖ ‖ 2 ⋮ **Reaction of 2-butyne with one molar equivalent of $\mathrm{HBr}$**: The addition of one molar equivalent of $\mathrm{HBr}$ to 2-butyne will result in a vinyl bromide, following Markovnikov's rule. ‖ ‖ 3 ⋮ **Reaction of 2-butyne with two molar equivalents of $\mathrm{HBr}$**: The addition of two molar equivalents of $\mathrm{HBr}$ will result in a geminal dibromide, with both bromine atoms on the same carbon atom. ‖ ∻Answer∻ ⚹ a. 2,3-dibromo-2-butene b. 2-bromo-2-butene c. 2,2-dibromo butane ⚹ ∻Key Concept∻ ⚹ Electrophilic addition to alkynes ⚹ ∻Explanation∻ ⚹ Alkynes undergo addition reactions with halogens and hydrogen halides, leading to the formation of dihalides or vinyl halides, depending on the amount of reagent used. ⚹ ∻Solution∻ ‖ 1 ⋮ **Propose a synthesis route**: To convert one organic molecule to another, we need to identify functional group transformations and appropriate reagents that can effect these changes. ‖ ∻Answer∻ ⚹ The synthesis route for a given conversion would require the starting material and the desired product to propose a specific route and reagents. ⚹ ∻Key Concept∻ ⚹ Synthesis route planning ⚹ ∻Explanation∻ ⚹ Planning a synthesis route involves identifying the necessary functional group transformations and selecting appropriate reagents and reaction conditions to achieve the desired product. ⚹◊What is the structural formula for the product formed when 2-pentene reacts with $HI$?⍭ Generate me a similar question◊

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