Question

Ketones $ \left( {{R_1}CO{R_2}} \right) $ ; $ {R_1} = {R_2}\; = \; $ alkyl group, can be obtained in one step by _________________.

Answer 1

Hint :R in organic compounds is a way of representing radical groups, which are basically groups of hydrogen and carbon atoms (among others, but mainly these) that bind to the atom it is attached to. Other atoms may be introduced, but the connecting atom has to be carbon. $ {R_1} $ and $R_2$ represent alkyl groups (single carbon with hydrogen atoms).

Complete Step By Step Answer:
We can prepare ketones by a number of different methods. Ketones can be made by oxidizing secondary alcohols with any available oxidizing agents. Ketones can also be produced by ozonolysis of disubstituted (two places) alkenes. Furthermore, ketones can also be synthesized through the Friedel-Crafts acylation of benzene or by oxymercuration-demercuration hydration of terminal alkynes.
But we require the process of preparation of ketone where it can be formed in a single step.
For this we use the method of secondary alcohol oxidation. This is a very easy process, but first we need to know what secondary alcohols are;
Secondary alcohols are a form of alcohol itself so it will have a hydroxyl group ( $ - OH $ ) but this group is attached to the carbon in between which has only a single atom of hydrogen situated on it. In other words, there will be two other $ R $ groups attached to the carbon along with the $ - OH $ group.
- So when any oxidizing agent, take for example potassium dichromate ( $ {K_2}C{r_2}{O_7} $ ) reacts on such secondary alcohols, what happens is that, they form chromate ester (which has a proton) in place of the hydroxyl group.
- But this stage only lasts for a very short period, because right after the chromate ester is formed, a base will quickly remove that proton which was there with the chromate ester. Remember that an ester is originally of this form: ( $ RCOOR' $ ).
- As a result of which the carbonyl group ( $ - \;C = O $ ) is formed after the original species of chromium leave the ester.
- The carbonyl group which is left after the reaction is one where one of the carbon atoms only has two alkyl groups and a carbonyl group attached to it.
- An organic compound with the above mentioned structure can only be classified as a ketone.
It happens in a single step, although there are background steps which do not last very long, like the formation of the ion of the oxidizing agent.
The reaction looks like this:
 $
  \;\;\;\;\;\;\;OH\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;O\;\;\;\;\; \\
  \;\;\;\;\;\;\;\;\;|\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;|\;| \\
  {R_1} - CH - {R_2}\;\xrightarrow[{{K_2}C{r_2}{O_7}/{H_2}O}]{{[O]}}\;{R_1} - C - {R_2} \\
  $

Note :
Ketones are named after their parent chain alkanes. The -e ending is dropped and -one is added in its place. The general (common) name for ketones is basically the 'alphabetical sequence of substituent groups + ketone'. Some of the most popular ketones have generic names which are used by laymen. For example, acetone is the generic name for the ketone, propanone.