Is the osmium oxidised or reduced during the formation of the osmate ester?

1 Answer
Jan 5, 2015

The osmium is reduced during the formation of the osmate ester.

A typical equation for the reaction is:

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Let's look at the oxidation numbers.

In cyclopentane, the oxidation number of each alkene carbon is 0. In the ester, the oxidation numbers are +1. The total oxidation number change in cyclopentane is +2.

The cyclopentane is oxidized, so the Os must have been reduced.

The cyclopentane loses two electrons. The Os gains two electrons — the new lone pair.

This decreases the oxidation number of Os from +8 to +6. Os is reduced.