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Carbonyl compounds

The simplest carbonyl compounds are ketones and aldehydes. A ketone has two alkyl (or aryl) groups bonded to the carbonyl carbon atom. An aldehyde has one alkyl (or aryl) group and one hydrogen atom bonded to the carbonyl carbon atom. Formaldehyde is the simplest aldehyde, with two hydrogen atoms bonded to the carbonyl group.

Aldehyde and Ketone

Ketones and aldehydes are similar in structure, and they have similar properties. In most cases, aldehydes are more reactive than ketones.

Why ketones and aldehydes have larger dipole moments than most alky halides and ethers?

Dipole

Nomenclature

When an aldehyde group can be named as substitutent? Name the prefix.

Substituents

Common Names

Questions

Answers a) 5-hydroxyhexan-3-one
b) 3-phenylbutanal
c) trans-2-methoxycyclohexanecarbaldehyde
d) 6,6-dimethylcyclohexa-2,4-dienone

Can ketones and aldehyde form hydrogen bonding?

Physical Properties

Question:
Arrange the following compounds in increasing order of their boiling points.

CH3CHO, CH3CH2OH, CH3OCH3, CH3CH2CH3

When secondary alcohols are oxidized we get ketones. Name the oxidizing agents used.

Ketones and Aldehydes

Over oxidation of primary alcohol leads to carboxylic acid, not aldehyde. How can we stop over oxidation?

synthesis_aldehyde

Question
How will you carry out the following conversion?
Ethanol to acetone

Concepts Recall
What is the structure of ethanol and acetone?

Tell the number of carbon atom in ethanol and acetone.

How will you convert alcohol to aldehyde?
Answer

Oxidation

What can you convert aldehyde to alcohol? How can you increase the number of carbon atoms in the produced alcohol?
Answer

By reduction and using Grignard reagent

How can you convert alcohol to ketone? Should we use primary or secondary alcohol to convert it to ketone.

Learning Haloform Reaction
Iodoform formula is $\ce{CHI3}$. Chloroform is analogous to iodoform. Can you draw the formula of chloroform?
Answer

$\ce{CHCl3}$

The haloform reaction is a chemical reaction where a haloform ($\ce{CHX3}$, where X is a halogen) is produced by the exhaustive halogenation of a methyl ketone (a molecule containing the $\ce{R-CO-CH3}$ in the presence of a base. R may be alkyl or aryl. The reaction can be used to transform acetyl groups into carboxyl groups or to produce chloroform ($\ce{CHCl3}$), bromoform ($\ce{CHBr3}$) or iodoform ($\ce{CHI3}$)

Now write down an example of Iodoform reaction.

Give the chemical test to distinguish between benzophenone and acetophenone

Concept Recall
Give the formula for benzophenone and acetophenone
Answer

Benzophenone $\ce{C6H5COC6H5}$ Acetophenone $\ce{C6H5COCH3}$

Now give the final answer to the question


Final Answer

Iodoform test

Elaborate with detail why you choose the answer

Arrange the following compounds in an increasing order of their reactivity in nucleophilic addition reactions: Ethanal, propanal, propanone, butanone.

Identify the point where nucleophilic attack occurs in case of aldehyde or ketone.

How can you increase the reactivity?

Answer

Reactivity depends on two factors, steric effect and electronic effect and electronic effect. Lesser the steric hindrance, higher the reactivity.

Final Answer

Butanone < propanone < propanal < ethanal

The nucleophilic addition of hydrogen cyanide to aldehydes and ketones


Aldehydes and ketones behave identically in their reaction with hydrogen cyanide
Hydrogen cyanide adds across the carbon-oxygen double bond in aldehydes and ketones to produce compounds known as hydroxynitriles
For example, with ethanal (an aldehyde) you get 2-hydroxypropanenitrile:
With propanone (a ketone) you get 2-hydroxy-2-methylpropanenitrile:

Note: When you are naming these compounds, don't forget that the longest carbon chain has to include the carbon in the -CN group. In both of the above examples, the longest carbon chain is 3 carbons - hence the "prop" in both names. The carbon with the nitrogen attached is always counted as the number 1 carbon in the chain.

The reaction isn't normally done using hydrogen cyanide itself, because this is an extremely poisonous gas. Instead, the aldehyde or ketone is mixed with a solution of sodium or potassium cyanide in water to which a little sulphuric acid has been added

Write the product of following reaction.

DIBAL (Di-isobutyl aluminum hydride)