Answer the following. Give a brief explanation why the answer you chose is corre

Question

Answer the following. Give a brief explanation why the answer you chose is correct.

1a). Reaction of (R)-(2-methyl-3-bromobutyl) benzene with sodium tert-butoxide gives two products as shown below.  Choose the best representation of the transition state of the reaction from the list below.

1b). Reaction of (R)-(2-methyl-3-bromobutyl) benzene with sodium tert-butoxide gives two products:

Of the two products, which is the minor product?
A. Product 1
B.  Product 2

1c). Reaction of (R)-(2-methyl-3-bromobutyl) benzene with sodium tert-butoxide gives two products:

What is the correct rate equation for this reaction?
A.  rate = [base][conjugate acid]
B.  rate = k[substrate][base]  
C.  raet = k[substrate][nucleophile]
D.  rate = k[conjugate base][conjugate acid]

Explanation / Answer

1a). TS3

Reason: tert-butoxide is a strong base and possess partial negative charge on it. The bromine atom is more electronegative atom than hydrogen atom hence bromine will possess partial negative charge on it and hydrogen will possess partial positive charge on it. Moreover thr Br & H must be in anti-periplanar arrangement to be elimination proceed. Br-C-C-H dihedral angle must be 180o.

1b). B.  Product 2

Reason: tert-butoxide is a strong base and bulkier also. It cannot abstract H+ from phenyl group adjacent methylene group due to steric hinderance. Hence it will abstract H+ from isopropyl group only. (Hoffman product rather than saytzeff product).

1c). B.  rate = k[substrate][base]

This is an E2 elimination reaction since we are using strong base tert-butoxide. It is a biomolecular reaction means concerted (one step only). Rate depends on both substrate and base. Nucleophiles are used in SN1 and SN2 reactions only not in elimination reactions.

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