Predict what type of kinetic isotope effect would be observed for the following.
ID: 850525 • Letter: P
Question
Predict what type of kinetic isotope effect would be observed for the following. Explain your reasoning and indicate which might give kH/kD values greater than 2. The * indicate the hydrogen atoms that are protium and deuterium for the studies.
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Predict what type of kinetic isotope effect would be observed for the following. Explain your reasoning and indicate which might give kH/kD values greater than 2. The * indicate the hydrogen atoms that are protium and deuterium for the studies.Explanation / Answer
a) first reaction signifies the secondary kinetic isotopic effect , because there is no bond to the isotopically added atom is broken. For the aforementioned nucleophilic substitution reactions, secondary hydrogen kinetic isotope effects at the ?-carbon provide a direct means to distinguish between SN1 and SN2 reactions. It has been found that SN1 reactions typically lead to large secondary kinetic isotope effects, approaching to their theoretical maximum at about 1.22, while SN2 reactions typically yield kinetic isotope effects that are very close to or less than unity. Kinetic isotope effects that are greater than 1 are referred to as normal kinetic isotope effects, while kinetic isotope effects that are less than one are referred to as inverse kinetic isotope effects. so for this reaction the insotopic effect number is less than 2.
b)in this reaction there is a bond cleavage of the isotopic atom, so this is called primary isotopic effect. in here the deuterium is larger in size compared to the hydrogen, which creates stearic hinderance for the bromine to approach. so in this reaction the rate of reaction will be faster if deuterium is replaced by the hydrogen. for this Kh / Kd will be greater than 2.