amines Flashcards

1
Q

what are amines

A

Amines constitute organic compounds derived by replacing one or more hydrogen atoms of ammonia molecule by alkyl/aryl group(s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the uses of amines in nature and humans

A

they occur among proteins, vitamins, alkaloids and hormones. Synthetic examples include polymers,
dyestuffs and drugs Two biologically active compounds, namely adrenaline and ephedrine both containing
secondary amino group, are used to increase blood
pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is Benadryl,

A

Benadryl, a well known antihistaminic drug also contains tertiary amino group.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is Novocain

A

Novocain, a synthetic amino compound, is
used as an anaesthetic in dentistry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the uses of Quaternary ammonium

A

Quaternary ammonium salts are used as
surfactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are Diazonium salts

A

Diazonium salts are intermediates in the
preparation of a variety of aromatic compounds including dyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

explain Structure of Amines

A

nitrogen atom of amines is trivalent and
carries an unshared pair of electrons. Nitrogen orbitals in amines are therefore, sp3 hybridized and the geometry
of amines is pyramidal. Each of the three sp3 hybridised orbitals of nitrogen overlap with orbitals of hydrogen or carbon depending upon the composition of the amines. The fourth orbital of nitrogen in all amines contains an unshared pair of electrons. Due to the presence of
unshared pair of electrons, the angle C–N–E
is less than 109.5°

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

__________ is the simplest example of arylamine.

A

C6H5NH2 or aniline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the bond angle in trimethylamine

A

108

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Amines are said to be
_______ when all the alkyl or aryl groups are the same, and ______
when they are different.

A

simple and mixed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Preparation of Amines

A

Reduction of nitro compounds
Ammonolysis of alkyl halides
Reduction of nitriles
Reduction of amides
Gabriel phthalimide synthesis
Hoffmann bromamide degradation reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Preparation of Amines by Reduction of nitriles

A

Nitriles on reduction with lithium aluminum hydride (LiAlH4) or catalytic hydrogenation produce primary amines. This reaction is
used for ascent of amine series, i.e., for preparation of amines containing one carbon atom more than the starting amine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Preparation of Amines by Reduction of nitro compounds

A

Nitro compounds are reduced to amines by passing hydrogen gas in the presence of finely divided nickel, palladium or platinum and also by reduction with metals in acidic medium. Nitroalkanes can
also be similarly reduced to the corresponding alkanamines.
Reduction with iron scrap and hydrochloric acid is preferred because FeCl2 formed gets hydrolyzed to release hydrochloric acid during the reaction. Thus, only a small amount of hydrochloric acid is required
to initiate the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Preparation of Amines by Ammonolysis of alkyl halides

A

the carbon - halogen bond in alkyl or benzyl halides can be easily cleaved by a nucleophile. Hence, an alkyl or benzyl halide on reaction with an ethanolic solution of ammonia undergoes nucleophilic substitution reaction in which the halogen atom is replaced by an amino (–NH2) group. This process of cleavage of the C–X bond by ammonia molecule is known as ammonolysis. The reaction is carried out in a sealed tube at 373 K. The primary amine thus obtained behaves as a nucleophile and can further react with alkyl halide to form secondary and tertiary amines, and finally quaternary ammonium salt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Preparation of Amines by Reduction of amides

A

The amides on reduction with lithium aluminium hydride yield amines.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Preparation of Amines by Hoffmann bromamide degradation reaction

A

Hoffmann developed a method for preparation of primary amines by
treating an amide with bromine in an aqueous or ethanolic solution of sodium hydroxide. In this degradation reaction, migration of an alkyl or aryl group takes place from carbonyl carbon of the amide to the nitrogen atom. The amine so formed contains one carbon less than that present in the amide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Preparation of Amines by Gabriel phthalimide synthesis

A

Gabriel synthesis is used for the preparation of primary amines. Phthalimide on treatment with ethanolic potassium hydroxide forms potassium salt of phthalimide which on heating with alkyl halide followed by alkaline hydrolysis produces the corresponding primary amine. Aromatic primary amines cannot be prepared by this method because aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Physical Properties of amines

A

The lower aliphatic amines are gases with fishy odour. Primary amines with three or more carbon atoms are liquid and still higher ones are solid. Aniline and other arylamines are usually colorless but get
coloured on storage due to atmospheric oxidation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why are Lower aliphatic amines are soluble in water?

A

Lower aliphatic amines are soluble in water because they can form hydrogen bonds with water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

solubility in amines

A

solubility decreases with increase in molar mass of amines due to increase in size of the hydrophobic alkyl part. Higher amines are essentially insoluble in water.

13
Q

the order of boiling points of isomeric amines is

A

Primary > Secondary > Tertiary

13
Q

what makes amines reactive

A

Difference in electronegativity between nitrogen and hydrogen atoms and the presence of unshared pair of electrons over the nitrogen atom makes amines reactive

14
Q

what decides the course of reaction of amines

A

The number of hydrogen atoms attached to nitrogen atom also decides the course of reaction of amines

15
Q

why amines behave as nucleophiles

A

amines behave as nucleophiles due to the presence of unshared electron pair

15
Q

Alkylation of amines

A

Amines undergo alkylation on reaction with alkyl halides

15
Q

Acylation of amines

A

Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. This reaction is known as acylation The products obtained by acylation reaction are known as amides The reaction is carried out in the presence of
a base stronger than the amine, like pyridine, which removes HCl so
formed and shifts the equilibrium to the right hand side

16
Q

what is benzoylation

A

Amines also react with benzoyl chloride (C6H5COCl). This reaction is known as benzoylation

16
Q

Carbylamine reaction

A

Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling substances. Secondary and tertiary amines
do not show this reaction. This reaction is known as carbylamine reaction or isocyanide test and is used as a test for primary amines.

16
Q

amines Reaction with nitrous acid

A

(a) Primary aliphatic amines react with nitrous acid to form aliphatic diazonium salts which being unstable, liberate nitrogen gas quantitatively and alcohols. Quantitative evolution of nitrogen is used in estimation of amino acids and proteins.
(b) Aromatic amines react with nitrous acid at low temperatures(273-278 K) to form diazonium salts, a very important class of
compounds used for synthesis of a variety of aromatic compounds

17
Q

amines Reaction with Benzenesulphonyl chloride

A

Benzenesulphonyl chloride (C6H5SO2Cl), which is also known as Hinsberg’s reagent, reacts with primary and secondary amines to form sulphonamides.
(a) The reaction of benzenesulphonyl chloride with primary amine
yields N-ethylbenzenesulphonyl amide The hydrogen attached to nitrogen in sulphonamide is strongly acidic due to the presence of strong electron withdrawing sulphonyl group. Hence, it is soluble in alkali.

17
Q

secondary amines Reaction with Benzenesulphonyl chloride

A

In the reaction with secondary amine, N,N-diethylbenzenesulphonamide is formed Since N, N-diethylbenzene sulphonamide does not contain any hydrogen atom attached to nitrogen atom, it is not acidic and hence insoluble in alkali.

18
Q

tertiary amines Reaction with Benzenesulphonyl chloride

A

Tertiary amines do not react with benzenesulphonyl chloride. This property of amines reacting with benzenesulphonyl chloride in a different manner is used for the distinction of primary, secondary and tertiary amines and also for the separation of a mixture of amines. However, these days benzenesulphonyl chloride is replaced by p-toluenesulphonyl chloride

18
Q

amine on Bromination

A

Aniline reacts with bromine water at room
temperature to give a white precipitate of 2,4,6-tribromoaniline

19
Q

what is the problem with amine on Bromination

A

The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their very high reactivity. Substitution tends to occur at ortho- and para-positions in order to control activating effect of –NH2
group This can be done by protecting the -NH2 group by acetylation with acetic
anhydride, then carrying out the desired substitution followed by hydrolysis of the substituted amide to the substituted amine.

19
Q

Nitration on amines

A

Direct nitration of aniline yields tarry oxidation products in addition to the nitro derivatives. Moreover, in the
strongly acidic medium, aniline is protonated to form the anilinium ion which is meta directing However, by protecting the –NH2 group by acetylation reaction
with acetic anhydride, the nitration reaction can be controlled and the p-nitro derivative can be obtained as the major product.

20
Q

Sulphonation on amines

A

Aniline reacts with concentrated sulphuric acid to form anilinium hydrogensulphate which on heating with sulphuric acid at 453-473K produces p-aminobenzene sulphonic
acid, commonly known as sulphanilic acid, as the major product.Aniline does not undergo Friedel-Crafts reaction (alkylation andacetylation) due to salt formation with aluminium chloride, the Lewis acid, which is used as a catalyst. Due to this, nitrogen of
aniline acquires positive charge and hence acts as a strong deactivating group for further reaction.

20
Q

what are DIAZONIUM SALT

A

The diazonium salts have the general formula –R N X2+where R stands for an aryl group and –X ion The N2+group is called diazonium group.

20
Q

Method Preparation of Diazonium
Salts

A

Benzenediazonium chloride is prepared by the reaction of aniline with nitrous acid at 273-278K. Nitrous acid is produced in the reaction mixture by the reaction of sodium nitrite with hydrochloric acid. The
conversion of primary aromatic amines into diazonium salts is known as diazotisation. Due to its instability, the diazonium salt is not generally stored and is used immediately after its preparation.

20
Q

Physical Properties of Diazonium
Salts

A

Benzenediazonium chloride is a colourless crystalline solid. It is readily soluble in water and is stable in cold but reacts with water when warmed. It decomposes easily in the dry state. Benzenediazonium fluoroborate is water insoluble and stable at room temperature

21
Q

Chemical Reactions Of Diazonium
Salts

A

Diazonium group being a very good leaving group, is substituted by other groups such as Cl –, Br–, I–, CN–and OH– which displace nitrogen from the aromatic ring. The nitrogen formed escapes from the reaction mixture as a gas

22
Q

Diazonium Salts Replacement by halide or cyanide ion

A

nucleophiles can easily be introduced in the benzene ring in the presence of Cu(I) ion. This reaction is called Sandmeyer reaction.
chlorine or bromine can also be introduced in the benzene ring by treating the diazonium salt solution with corresponding
halogen acid in the presence of copper powder. This is referred as Gatterman reaction The yield in Sandmeyer reaction is found to be better than
Gattermann reaction

22
Q

Diazonium Salts Replacement by iodide ion

A

Iodine is not easily introduced into
the benzene ring directly, but, when the diazonium salt solution is treated with potassium iodide, iodobenzene is formed

23
Q

Diazonium Salts Replacement by fluoride ion

A

When arenediazonium chloride is
treated with fluoroboric acid, arene diazonium fluoroborate is precipitated which on heating decomposes to yield aryl fluoride.

24
Q

Diazonium Salts Replacement by H:

A

Certain mild reducing agents like
hypophosphorous acid (phosphinic acid) or ethanol reduce diazonium salts to arenes and themselves get oxidised to phosphorous acid and ethanal, respectively

25
Q

Diazonium Salts Replacement by –NO2
group:

A

When diazonium fluoroborate is heated with aqueous sodium nitrite solution in the presence of copper, the diazonium group is replaced by –NO2 group.

25
Q

Diazonium Salts Replacement by hydroxyl group:

A

If the temperature of the diazonium salt solution is allowed to rise upto 283 K, the salt gets hydrolysed to phenol

26
Q
A
27
Q
A
28
Q
A