The relative reactivity of the 1 degree: 2 degree: 3 degree hydrogens of (CH_3)_
ID: 503806 • Letter: T
Question
The relative reactivity of the 1 degree: 2 degree: 3 degree hydrogens of (CH_3)_3 CCH_2 CH_3 in free radical chlorination is 1: 3.8: 5.0. Provide the structure of each monochlorination product, and estimate the relative amount of each in the mixture of monochlorinated products. What is the relative reactivity of 2 degree vs 1 degree hydrogens in the free radical brominating of n-butane if the ratio of 1-bromobutane to 2-bromobutane formed is 7.93? Which of the following statements is the best statement of the Hammond Postulate? In an endothermic reaction, the transition state is closer to the reactants in structure. In an exothermic reaction, the transition state is closer in energy to the products. Related species that are similar in energy are also similar in structure.Explanation / Answer
Answer for 96.
Percentage of monochlorination products estimation on free radical chlorination: ([number of hydrogens] × [ratio factor]) / [(primary hydrogens × 1) + (secondary hydrogens × 3.8) + (tertiary hydrogens × 5)] .
Denominator total = 9 + (2x3.8) + 3 = 19.6
ClCH2(CH3)2CCH2CH3: 9/19.6 = 45.9%
(CH3)3CCHClCH3: 7.6/19.6 = 38.8%
(CH3)3CCH2CH2Cl: 3/19.6 = 15.3%
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Answer for 97.
Ratio of 1-bromobutane and 2-bromobutane: 7:93
Structure of 1-bromobutane: CH3CH2CH2CH2Br
Structure of 2-bromobutane: CH3CH2CHBrCH3
To calculate relative reactivity we need to find yield per C-H bond in each compound:
Total number of primary hydrogens = 6; Total yield of 1-bromobutane = 7%
Therefore 7/6 = 1.16 is yield per C-H bond on primary hydrogens
Total number of secondary hydrogens = 4; Total yield of 2-bromobutane = 93%
Therefore 93/4 = 23.25 is yield per C-H bond on secondary hydrogens
Relative reactivity of 2o vs 1o hydrogens in bromination of n-butane is 23.25/1.16 = 1:20
Answer for 98.
Statement C is best statement for Hammond postulate.
In an exothermic reaction the structure and energy of transition state is closer to that of reactant's. In an endothermic reaction the structure and energy of transition state is closer to that of products'.