OCHEM rxn sequences

[joonkimdds]

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Hello guys~ I need help with these. I know that they are many but I would appreciate it if you guys can help at least one of them 🙂

A. I think KMnO4 will change OH into COOH and then NH3 will use nucleophilic addition to carbonyl carbon. I don't know what OBr- does.

B. I think PBr3 changes OH into Br and then we got primary alkyl with NaCN. Which reaction is it? E1, or Sn2? I don't think it's E2 and SN1 because they prefer tertiary. If it's elimination rxn, then it forms alkene so H2,Ni will break the double bond and form C-C but if it's SN2 then I don't know what H2, Ni can do. Is Ni same as Pt and Pd when it's with H2?

C. I don't think NH4 can do anything.

D. I don't know what Cu does.

E. I think CN will replace OH. I don't know what H2O can do to it and what NH3 will do afterward.


Thanks :~! 🙂

 

[ethanyoo726]

The answer is A.

Explanation: Hofmann Rearrangement.

1) KMnO4 changes the compound into a carboxylic acid.
2) NH3 changes the carboxylic acid into an amide.
3) -OBr is a strong base which causes a Hofmann Rearrangement leaving you with an aniline.

Whenever you have a primary amide and a strong base with a halogen...you get Hofmann Rearrangement.

 

[joonkimdds]

The answer is A.

Explanation: Hofmann Rearrangement.

1) KMnO4 changes the compound into a carboxylic acid.
2) NH3 changes the carboxylic acid into an amide.
3) -OBr is a strong base which causes a Hofmann Rearrangement leaving you with an aniline.

Whenever you have a primary amide and a strong base with a halogen...you get Hofmann Rearrangement.

I thought Hoffman rearrangement happens only if we have Br2 with OH.
I guess I have to memorize what you said. A strong base + halogen + primary amide.


p.s. can someone also answer the other questions?

 

[nze82]

I don't think every single choice should give you a product! They might be wrong choices, because they don't give you a product at all. But here's what choice B will end up giving you:

Ph-CH2-OH -PBr3-> Ph-CH2-Br -NaCN-> Ph-CH2-CN (SN rxn) -H2,Ni->

Ph-CH2-CH2-NH2