What is the preparation for butanoic acid

Carboxylic acid

Carboxylic acid is an organic acid that contains a carboxy functional group. This group consists of a carbonyl and a hydroxyl group. The structural formula for carboxylic acid looks like this:

Carboxylic acid topics on this page

Melting and boiling points of carboxylic acid

With carboxylic acids, as with all molecules, there are van der Waals interactions. The strength of these interactions is determined by the same influences that we have already determined for hydrocarbons.

In addition, carboxylic acids, like alcohols, can form hydrogen bonds. The hydrogen bonds are higher in carboxylic acids than in alcohols of the same chain length, since both the free electron pairs of the oxygen atom of the carbonyl group and the free electron pairs of the oxygen atom of the hydroxyl group can interact with a positively polarized hydrogen atom. Therefore, the melting and boiling points of carboxylic acids are higher than those of the corresponding alcohols.

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Solubility of carboxylic acid

The solubility of carboxylic acids, like that of aldehydes, depends on the length of the non-polar organic residue.

Acidity (influence of substituents)

Carboxylic acids are Brönsted acids - i.e. proton donors. The carboxy group can donate a proton, creating a carboxylation.

But why is this proton given off so easily, in contrast to the proton of the hydroxyl group of alcohols?
There is one more mesomeric boundary structure for the resulting carboxylation than for the corresponding carboxylic acid, which is why the deprotonated molecule is more stable.

The strength of the carboxylic acid (colloquially: how easily the proton can be released) depends on the test on the carboxy group. For this test we compare three different carboxylic acids:

Monochloroethanoic acid

We see an inductive effect, which pulls electrons out of the carboxy group. The electron density is lower, which makes the oxygen atom of the hydroxyl group less likely to share its electrons. As a result, the proton is more easily split off, since the binding electron pair no longer has to be divided.

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Methanoic acid

The rest (the hydrogen atom) has no effect.

Ethanoic acid

The rest here has a + I effect, which pushes electrons into the carboxy group. The electron density is higher, which makes the oxygen atom of the hydroxyl group more willing to share its electrons. It follows that the proton does not necessarily have to be split off.

In general, the following rule can be drawn up: A residue with an -I effect increases the acidity of a carboxylic acid. A residue with a + I effect reduces the acidity. The stronger the -I effect, the higher the acidity. The stronger the + I effect, the lower the acidity.

Reaction behavior of carboxylic acids

Carboxylic acids can react with alcohols with a condensation reaction to form esters. This reaction is also called esterification.

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