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Can anyone tell me where I am doing it wrong for the following reaction? enter image description here

In the first step, Br should be attached to the alpha carbon.

In second step, the bromide is replaced by cyanide.

I am able to get the third product that is final compound.

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  • $\begingroup$ Heating a carboxylic acid often leads to decarboxylation. So decarboxylate your product from step 2 (well actually the product formed following acidification in step 3!) $\endgroup$ – Leeser Jul 21 '16 at 12:26
  • $\begingroup$ @Leeser can you tell me the products formed $\endgroup$ – user32086 Jul 21 '16 at 12:31
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Step 1: $\alpha$-bromination $$\ce{CH3-COOH + Br2/P -> Br-CH2-COOH}$$

Step 2: Nucleophilic Substitution by Sodium Cyanide $$\ce{Br-CH2-COOH + NaCN -> NaBr + NC-CH2-COOH}$$

Step 3: Acid-catalyzed Conversion of Nitrile to Amide or Acid

(1) First hydration... $$\ce{NC-CH2-COOH + H2O -> H2N-CO-CH2-COOH}$$ (2) Further heating... $$\ce{H2N-CO-CH2-COOH -> HOOC-CH2-COOH + NH4+}$$

Special Notes

Be VERY CAREFUL with Step 2 as you are potentially forming $\ce{HCN}$ which could get everyone in the lab killed if you're not careful.

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  • $\begingroup$ But @sixtytrees has made different products $\endgroup$ – user32086 Jul 21 '16 at 12:41
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    $\begingroup$ @user123733 No, he only went step further with decarboxylation, without any good reason. $\endgroup$ – Mithoron Jul 21 '16 at 13:43
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There are two possibilities. You will have a two step reaction

NC-CH2COOH -> HOOC-CH2-COOH This is malonic acid. It can be further decarboxylated to

HOOC-CH2-COOH + H$^+$ + heat -> CO2 + CH3COOH

the final product is acetic acid.

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