A carbonyl functional group, C=O, is introduced into aldehydes and ketones. Both are organic compounds of -CHO and RC(=O)R’ structures, where R and R’ are, respectively, carbon-containing substituents.
- What are Aldehydes?
- What are Ketones?
- Occurrence of Aldehydes and Ketones
- Uses of Ketones and Aldehydes
- Aldehydes and Ketones in Class 12
- Illustrated Examples
- FAQs on Aldehydes and Ketones
What are Aldehydes?
In aldehydes, one hydrogen atom is bound to the carbonyl group and either a second hydrogen atom or a hydrogen group that may be an alkyl group or one that comprises a benzene ring.
What are Ketones?
The carbonyl group of ketones has two groups of hydrocarbons attached to it. These may be either benzene rings or alkyl groups found in them. Ketone does not have a carbonyl group attached to the hydrogen atom.
The methanoyl or formyl group is also called aldehydes and ketones. There are 2 remaining bonds in this group’s carbon atom that may be occupied by aryl or alkyl or substituents. The compound is a ketone if none of these substituents is hydrogen. If at least one is hydrogen, then an aldehyde is the compound.
Occurrence of Aldehydes and Ketones
Aldehydes and ketones are commonly used in nature in conjunction with other functional groups. They are mainly present in microorganisms or plants and substances such as cinnamaldehyde (cinnamon bark), vanillin (vanilla bean), Citra (lemongrass), helminthosporium (a fungal toxin), carvone (spearmint and caraway), camphor (camphor trees).
Uses of Ketones and Aldehydes
- For the manufacture of acetic acid and pyridine derivatives, acetaldehyde is used to a great degree.
- In perfumes, beauty products, and colourants, benzaldehyde is used. It is applied and often used as a bee repellent to give almond flavour to food items.
- Acetone is used in the kitchen as a nail polish remover and paint thinner.
- It is used for chemical peeling and acne procedures in medicine.
Aldehydes and Ketones in Class 12
This concept is taught in chapter ‘Aldehydes, Ketones And Carboxylic acids.’ You will learn about the structures, preparation, and different reactions of aldehydes and ketones. The chapter carries 28 marks.
1. Do silver mirror tests cover ketones?
Solution: An aldehyde is oxidised into the resulting carboxylic acid by Tollens' reagent. Tollens' reagent does not oxidise ketones, so preparing a ketone in a glass test tube with Tollens’ reagent does not result in a silver mirror.
2. Is formaldehyde a type of aldehyde?
Solution: It is the simplest of the (R-CHO) aldehydes.
3. Are aldehydes electrophilic?
Solution: Aldehydes are a broad class of electrophilic carbonyl compounds which replace the carbonyl carbon atom with at least one hydrogen atom.
FAQs on Aldehydes and Ketones
Q: How are ketones and aldehydes different?
Q: Why are aldehydes more responsive than ketones to nucleophilic substitutions?
Q: Why are the ketones’ boiling points greater than those of aldehydes?
Q: Can ketones be analysed by Fehling’s solution?
Q: Are aldehydes poisonous for humans?