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17 Reactions of Aromatic Compounds -- Part 19
The aromatic rings are activated by OH groups and the carboxylic acid groups.
COO- ) groups on the molecule to promote solubility in water and to help bind the dye to the polar surfaces of cotton and wool.
It is common.
Most of the methods derive from the reactions of amine.
Adding another alkyl group is one of the most common amine syntheses.
The process converts ammonia to a primary amine, or a primary amine to a secondary amine, or a tertiary amine.
Aeductive amination is a two step process.
We form an imine or oxime derivative of a ketone or aldehyde and then reduce it to amine.
A alkyl group is added to the nitrogen atom.
Depending on the starting amine, the product can be a primary, secondary, or tertiary amine.
condensation of hydroxylamine with a ketone or an aldehyde leads to reduction of oxime.
Most oximes are stable, so Hydroxylamine is used in place of ammonia.
The oxime can be reduced using zinc and HCl.
Imine is a Schiff base.
A secondary amine is given when the imine is reduced using either LiAlH4 or NaBH4.
An iminium salt is given by the condensation of a secondary amine with a ketone or aldehyde.
Iminium salts are rarely isolated.
The reducing agent reduces the iminium salt to a tertiary amine.
The reducing agent has to reduce the iminium salt but not the carbonyl group.
It reduces the imine faster than the carbonyl group, and it is less reactive than sodium borohydride.
The older, more toxic reagent, NaBH3CN, has largely been replaced by the newer, more benign reagent, sodium triacetoxyborohydride.
Reductive amination shows how to synthesise the following amine from the indicated starting materials.
Adding a cyclopentyl group to aniline is required to make a ketone.
The compound is called cyclopentanone.
The compound is called acetaldehyde.
Show how to synthesise the following amines from the indicated starting materials.
Acylation-reduction adds one alkyl group to the starting amine.
An amide is less nucleophilic and unlikely to over-acylate, which is the result of acylation of the starting amine.
The amine is given by the reduction of the amide.
Ammonia can be converted to a primary amine, a secondary amine, or a tertiary amine.
Using acylation-reduction, ethylpyrrolidine was used.
Adding an ethyl group is required to make a tertiary amine.
The group added acid chloride will be acetyl chloride.
If you compare this synthesis with the Solved Problem 19-5(b) you will see how reductive amination and acylation-reduction can accomplish the same result.
Primary amines are used as starting materials for synthesis of secondary and tertiary amines.
Many methods have been developed for making primary amines.
We will look at some of the more common ones.
There is a tendency for over alkylation to form a mixture of monoalkylated and polyalkylated products.
Simple primary amines can be synthesised by adding a halide or tosylate to a large amount of ammonia.
The probability that a molecule of the halide will alkylate ammonia is larger than the probability that it will over-alkylate the amine product.
A mixture of heptan-1-amine, dialkylamine, and trialkylamine can be added to 1-bromoheptane.
There is a way to show how this reaction takes place.
The phthalimide anion is a strong nucleophilic and can be tosylate or replaced with a halide.
The very stable, aromatic hydrazide of phthalimide is given whenalkyl phthalimide with hydrazine displaces the primary amine.
Gabriel used the anion of phthalimide to put the nitrogen atom into a primary amine.
A good nucleophile that can only alkylate once is what we need.
The azide ion and the cyanide ion are good for introducing a nitrogen atom.
The products have no tendency to react further.
Azides can be reduced by either LiAlH4 or catalytic hydrogenation.
Alkyl azides can be reduced without purification.
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