ALDEHYDES/ KETONES/ CARBOXYLIC ACIDS Flashcards
What is an aldehyde?
How are they named?
One carbon and one hydrogen attached to the carbonyl carbon atom
They are named by replacing the terminal -e suffix of the corresponding alkane with -al
The parent chain must contain the -CHO group which is always numbered 1
What are ketones?
How are they named?
A ketone has 2 carbon atoms attached to the carbonyl carbon
They are named by replacing the terminal -e of the corresponding alkane with -one, the parent chain is the longest on that contains the ketone group and numbering begins at the end nearer the carbonyl carbon
In naming compounds that contain more than 1 functional group, IUPAC has established an order of precedence, list in order of highest to lowest:
- Carboxyl group (-oic acid)
- Aldehyde group (-al)
- Ketone Group (-one)
- Alcohol group (-ol)
- Amino group (-amine)
- Sulfhydryl (-thiol)
List some physical properties of aldehydes and ketones
Both are polar
interact in the pure state by dipole-dipole interactions, as a result they have higher BP than non polar compounds with comparable number of electrons
intermediate boiling points
Comment on the polarity of aldehydes and ketones
Aldehydes and ketones have very reactive groups due to the polarity and structure of the carbonyl group
Aldehydes are usually more reactive than ketones
What happens when you oxidise an aldehyde?
They become carboxylic acids (CH => COH)
Explain a reduction reaction in both aldehydes and ketones:
both are reduced to an alcohol group by hydrogen and in the presence of a transition-metal catalyst
Reduction of an aldehyde gives a primary alcohol
Reduction of a ketone gives a secondary alcohol
What is a carboxylic acid?
A carboxylic acid has an -OH group attached directly to the carbonyl carbon atom C=O
The functional group of a carboxylic acid is a carboxyl group, which can be represented in any one of 3 ways:
O=C-O-H
- COOH
- CO2H
How to name carboxylic acids?
For the IUPAC name drop the final -e from the parent alkane and replace it with the suffix -oic acid
A carboxyl group takes precedence over most other functional groups, including hydroxyl and amino groups, as well as the carbonyl groups of aldehydes and ketones
Number the chain beginning with the carbon of the carboxyl group, because the carboxyl carbon is understood to be carbon 1, there is no need to give it a number
How to name a dicarboxylic acid?
add the suffix -dioic acid to the name of the parent alkane that contains both carboxyl group; thus -ane becomes -anedioic acid
The numbers of the carboxyl carbons are not indicated because they can only be at the end of the chain
Define some of the physical properties of carboxylic acids
- the carboxyl group contains 3 polar covalent bonds (C=O, C-O, and O-H), this polarity determines the major physical properties
- carboxylic acids have significantly higher BP than other types of organic compounds comparable molecular weight
- Carboxylic acids are more soluble in water than alcohols, ethers, aldehydes, and ketones of comparable molecular weight
Explain carboxylic acid reactions with bases
All carboxylic acids, whether soluble or insoluble in water, react with NaOH, KOH, and other strong bases to form water soluble salts
Explain decarboxylation
The loss of CO2 from a carboxyl group, almost all carboxylic acids, when heated to a very high temperature, will undergo thermal decarboxylation
Explain Fischer Esterification
One of the most commonly used methods for the preparation of esters
A carboxylic acid is reacted with an alcohol in the presence of an acid catalyst, most commonly concentrated sulfuric acid (reversible reaction)
Alcohol adds to the carbonyl group of the carboxylic acid to form a tetrahedral carbonyl addition intermediate, the intermediate then loses H2O to give an ester
