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Deuterium (D) is the isotope of hydrogen of mass number 2, with a proton and a neutron
Chapter 7, Problem 7-75(choose chapter or problem)
Deuterium (D) is the isotope of hydrogen of mass number 2, with a proton and a neutron in its nucleus. The chemistry of deuterium is nearly identical to the chemistry of hydrogen, except that the CD bond is slightly (5.0 kJ>mol, or 1.2 kcal>mol) stronger than the CH bond. Reaction rates tend to be slower if a CD bond (as opposed to a CH bond) is broken in a rate-limiting step. This effect on the rate is called a kinetic isotope effect. (Review 4-57.) (a) Propose a mechanism to explain each product in the following reaction. 3 CHCH CH3 CH2 CH CH3 Br 3 CHCH CH3 OH KOH, alcohol elimination product substitution product + (b) When the following deuterated compound reacts under the same conditions, the rate of formation of the substitution product is unchanged, while the rate of formation of the elimination product is slowed by a factor of 7. 3 CHCD CD3 Br KOH, alcohol CD2 CH CD3 3 CHCD CD3 OH seven times slower rate unchanged + Explain why the elimination rate is slower, but the substitution rate is unchanged. (c) A similar reaction takes place on heating the alkyl halide in an acetone>water mixture. 3 CHCH CH3 CH2 CH CH3 Br 3 CHCH CH3 OH water/acetone heat elimination product substitution product + Give a mechanism for the formation of each product under these conditions, and predict how the rate of formation of each product will change when the deuterated halide reacts. Explain your prediction. water/acetone heat 3 CHCD CD3 Br CD2 CH CD3 3 CHCD CD3 OH rate changed? rate changed?
Questions & Answers
QUESTION:
Deuterium (D) is the isotope of hydrogen of mass number 2, with a proton and a neutron in its nucleus. The chemistry of deuterium is nearly identical to the chemistry of hydrogen, except that the CD bond is slightly (5.0 kJ>mol, or 1.2 kcal>mol) stronger than the CH bond. Reaction rates tend to be slower if a CD bond (as opposed to a CH bond) is broken in a rate-limiting step. This effect on the rate is called a kinetic isotope effect. (Review 4-57.) (a) Propose a mechanism to explain each product in the following reaction. 3 CHCH CH3 CH2 CH CH3 Br 3 CHCH CH3 OH KOH, alcohol elimination product substitution product + (b) When the following deuterated compound reacts under the same conditions, the rate of formation of the substitution product is unchanged, while the rate of formation of the elimination product is slowed by a factor of 7. 3 CHCD CD3 Br KOH, alcohol CD2 CH CD3 3 CHCD CD3 OH seven times slower rate unchanged + Explain why the elimination rate is slower, but the substitution rate is unchanged. (c) A similar reaction takes place on heating the alkyl halide in an acetone>water mixture. 3 CHCH CH3 CH2 CH CH3 Br 3 CHCH CH3 OH water/acetone heat elimination product substitution product + Give a mechanism for the formation of each product under these conditions, and predict how the rate of formation of each product will change when the deuterated halide reacts. Explain your prediction. water/acetone heat 3 CHCD CD3 Br CD2 CH CD3 3 CHCD CD3 OH rate changed? rate changed?
ANSWER:Step 1 of 4
In organic chemistry, the reactions consist mainly of two types substitution and elimination reaction. The substitution reaction involves replacing one group with the other group. While in the elimination reaction, one group is eliminated to form a double bond.