5
$\begingroup$

When oxidising primary alcohols, $\ce{K2Cr2O7}$ is used because it's a useful & readily available oxidising agent.

Why does the sulfuric acid need to be added? Does it have to do with the acidity of the resulting dichromate solution? How would this facilitate the oxidation?

$\endgroup$
1
  • 1
    $\begingroup$ Low pH raises oxidation potential, AFAIK. $\endgroup$
    – Mithoron
    Commented Apr 13, 2016 at 22:00

1 Answer 1

5
$\begingroup$

It protonates the chromic acid to form an oxonium ion, increasing positive charge at the chromium center.

Using $\ce{H^+}$ typically protonates the electrophile, making it more electrophilic (more electron deficient = more electrophilic), just like with acid-catalyzed esterification. In fact, you're making a chromate ester in this reaction.

See the first step here in this image (and the rest is related, also):chromic acid oxidation mechanism Image source

$\endgroup$
1
  • $\begingroup$ Also, it apparently helps break the dichromate ion into two chromic acid molecules. $\endgroup$ Commented Apr 14, 2016 at 1:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.