Dimethoxytrityl Is Used as a Protecting Group on the 5'-OH

question 37

Multiple Choice

Dimethoxytrityl is used as a protecting group on the 5'-OH of the carbohydrate in the synthesis of DNA.What is the species formed upon cleavage with acid? What factors contribute to its stability?

• A)A dimethoxymethyl cation is formed.The cation is stabilized by hyperconjugation and by the donor effect of the OCH₃ groups.
• B)A carbanion is formed and this is stabilized by resonance of the benzene rings and by the inductive effect of the OCH₃ groups.
• C)A carbocation is formed and this stabilized by inductive effect of the OCH₃ groups as well as by resonance of the negative charge on the benzene ring.
• D)A dimethoxytrityl cation is formed.The cation is stabilized by resonance of the benzene rings and by the donor effect of the OCH₃ groups.
• E)A neutral dimethoxytrityl is formed.The lack of charge contributes to the easy of hydrolysis and the stability of the species released.

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