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Aldehyde Ketones

Essay by   •  November 19, 2012  •  Essay  •  452 Words (2 Pages)  •  1,045 Views

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Aldehydes are made by oxidizing primary alcohols so that they don't get further oxidized into carboxylic acid you need to use an excess amount of alcohol so that there isn't enough oxidizing agent to make further oxidation of aldehyde. Another way to secure that aldehyde would be to remove it from the mixture right when its formed before it is oxidized. To obtain ketones you need to oxidize secondary alcohols and because they don't have a hydrogen attached to its carbonyl group like aldehyde you don't need to remove it from the mixture as it would take a strong oxidizing agent able to break the carbon-carbon bonds to oxidize it further.

When bonding, the slight positive charge of the carbon in the carbonyl group attracts negatively charged ions such as CN- or the slightly negatively charged part of a molecule, for example the lone pair on a nitrogen in ammonia NH3 . When this occurs the carbon-oxygen bond is broken and the carbonyl group undergoes an addition reaction where it often results in the loss of a water molecule.

The results from these addition reactions are two functional groups. You can get an -OH group that behaves like a simple alcohol and can be replaced later by chlorine that is replaced later by an -NH2 group. The second functional group can be a -CN group that is converted into a carboxylic acid group. Amino acids used to construct proteins can be made from these replacements as is shown below.

Aldehydes and ketones can be used to create complicated alcohols easily. They just have to react with a Grignard reagent which has the formula RMgX where R is an alkyl or aryl group and X is a halogen. The bonding is with the carbon-oxygen double bond in the carbonyl group so both aldehydes and ketones react the very same way with this reagent. In the first stage the Grignard reagent adds across the carbon-oxygen double bond and then dilute acid is added to the product to hydrolyze it.

The form of alcohol made depends on the carbonyl compound you started with. Lets say you were to try to make a primary alcohol, in that case you could use methanal which is also the simplest aldehyde.

So using methanal as you break the carbon-oxygen double bond you add an alkyl grounp to that carbon and the oxygen is bonded with a hydrogen which is attracted to its pull. The molecule CH3CH2CH2OH is a primary alcohol and you can see there's an alkyl group attached to the carbon, as well as two hydrogen atoms and also -OH which could make this a possible product if you were to use methanal.

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