reaction mechanism

Question 1

arndt-eistert reaction

Answer 1

type of homologation reaction in which the higher analog of carboxylic acids are produced in the presence of thionyl chloride, silver oxide, and azomethylene

Question 2

arndt-eistert reaction mechanism

Answer 2

1- formation of acyl chloride:
the -COOH reacts with SoCl2 to create acyl chloride, and SO2, and HCl as by product
2- attak of azomethylene:
azomethylene nucleouphilicaly attacks on the carbonyl carbon to form unsable intermediate diazoketone
3- removal of nitrogen gas:
Nitrogen gas and HCL is removed to form carbocation in the presence of silver oxide
4- rearrangement of carbocation
the carbocation undegoes rearragement of form ketene which then reacts with water to form carboxylic acid with the addition of -CH2 unit

Question 3

application of arndt-estert reaction

Answer 3

1- mostly occurs in acid
2- reaction is used to convert alpha-amino acid into B-amino acid
3- nonadecanoic acid, eicosanoic acid, heneicosanoic acid are synthesized by stearic acid in good yeilds by this method
4- UV absorption maxima for some diazoketones derived from higher memebers of aliphatic, carboxylic acids series are recorded.
5- efficiant way of purification of synthetic products

Question 4

Bayer-villiger reaction

Answer 4

reaction in which aldehydes and ketones can be oxidised by the action of peracids and peroxyacids to form esters

Question 5

Diels Alder reation

Answer 5

reaction in which cycloaddition takes place when a conjugated substane is reacted with a compound containig double bond and heated in a solvent to form rigng system.
it is a type of addition reaction
conjugated system is alled dience, compound containing double bond is called dienophile, and ring system formed is called adduct

Question 6

application of diels alder rection

Answer 6

-it is used in preparation of steroids such as cortisone, cholestrol, vitamin D, etc
-used in synthesis of prostaglandins F2A and E2
-synthesis of natural and un-natural polyheterocycles and polycarbocycles

Question 7

wolff krishner reaction

Answer 7

reaction in which aldehyde or ketone is heated with hudrazine and strong base (in the presence of dimethylene glycol as solvent), the carbonyl group is reduced to methylene group/alkane

Question 8

mechanism of wolff krishner

Answer 8

step 1- formation of hydrazone
the ketone reacts with hydrazine, the C=O is replaced by C=N by the elimination of H2O molecule to form hydrazone
step 2- attak of base
the base (OH-) extracts to form water moleule and then anion is formed from hydrazone which then undegoes delocalization to form its stable canonical form.
step 3- Attack of water as nucleophile
the stable canonical form extract the hydrogen from nuclephile (water) and another hydrogen is again removed by the base
step 4- removal of nitrogen gas
from the unstable anion, the nitrogen gas is removed to form a carbonion which again takes hydrogen from H-OH (nucleophile) to form the final product called alkane.

Question 9

appications of wolff krishner reaction

Answer 9

-has been widely utilized to convert carbonyl groups to methylene group
-used in synthesis of pyrroles
-for reduction of camphor to comphane

Question 10

Freidl-krafts alkylation

Answer 10

reaction by which an alkyl group is introduced to the benzene ring is knowns as….. in the reaction an aromatic compound is treated with an alkyl halide in the presence of a lewis acid such as AlCl3, FeCl3, or certain other metal halides to form an alkyl substituted benzene ring

Question 11

friedl-krafts alkylation steps

Answer 11

step 1- formation of electrophile
the alkyl halides are reacted with the lewis acid (AlCl3) to form a strong electrophile or alkyl carbocation. this alkyl carbocation is actually the alkylaing species.
step 2- attak of electrophile on benzene ring
this electophile (alkylating species) attack on benzene ring to form unstable interediate which then form alkylated benzene. the catalyst is regenrated at the end and the product is formed

Question 12

freidels carfats acylation

Answer 12

reaction in which an acyl goup is introduced o the benzene ring by means of acid halide or acid anhydride in he presence of lewis acid

Question 13

steps of FC acylation

Answer 13

step 1- fomation of strong eletrophile
the acyl chloride reacts with AlCl3 to form a complex which then decomposes to form arylium ion, the actual acylating species
step 2- attach of acylating species
the benzene reacts with electrophile. to form unstable intermediate which then decomposes to form keto-benzene and the catalyst is regenerated

Question 14

application of FC reaction

Answer 14

-one of the most impotant use of these two reaction is that it is used in the production of dyes, like xanthene, dyes and thrymphthalein (indicator)
-it is also used in haworth reaction
-it is used in syntheseizing substitued aromatic compounds
-these reaction provides greater control over the reaction poducts

Question 15

canizzaros reaction

Answer 15

reation in which two aldehydes withouth alpha hydrogens are treated with a cold concentrated aqeuos alkali, they undergo dispropotionation (self oxidation and reaction) such that are aldehyde is oxideized to form
-COOH and the second aldehyde is reduced to form primarily alcohol

Question 16

steps of canizzaros reaction

Answer 16

1- attack of base
initially, the bases attaks on the carbonyl carbon of aldehyde to form anion
2- formation of acid
they hydride ion is released from the anion and is oxidized to form formic acid
3- addition of hydride ion-
the previous hydride ion is transfered to the second aldehyde and reduced to form methory ion
4- formation of products
the oxidised aldehyde i.e formic acid reacts with NaOH to for carboxylate salt and the reduced methoxy ion reacts with the hydrogen to form primary alcohol.

Question 17

canzzaros reaction applications

Answer 17

-neopentyl glycol is used in polyestor for resin used in airplanes
-it is also used as varnish coating, synthetic lubicants, and plasctcites
-formation of acid and alcohols ascribed to direct CO2 reduction products

Question 18

perkins reaction

Answer 18

perkins condensation is a condensation of an aromatic aldehyde and acetic anhydride prodcing alpha, beta- unsaturated products

Question 19

apllication of perkin reaction

Answer 19

-for the synthesis of cnnamic acid in lab. cinnamic acid are naturally occuring unsaturated carboxylic acids that are found commonly in cinnamon and shea butter
-convertion of furfural into furylacyrlic acid
-formation of coumaric acid from salicylaldehyde, which on dehydration yeilds coumarin
-synthesis of phytoestrogenic stilbene resveratol

Question 20

pekins reaction steps

Answer 20

1- formation of carbon anion
the acetate ion from the sodium acetate react with acetic anhydride to form acetic acid and carbanion
2- attack of carbonyl carbon of benzaldehyde
carbanion reatcs on carbonyl carbon of benzldehyde to form an intermediate anion
3-addition of hydrogen
the hydrogen from water adds nuclepillically to stabiize the anion
4-elimination of water
dehydration occurs and double bond is introduced between carbon atoms
5- hydrolysis
hydrolyis occur in compound and bond breaks to form final products i.e. cinnamic acid and acetic acid

Question 20

mannich reaction steps

Answer 20

1- preparation of iminium ion
the lone pair of the secondary amine on nitrogen atom attacks on he carbonly carbon of fomaldehyde to form iminium ion
2- hydrogenation
H atom attacks on the oxygen atom to make the nitrogen stable and remove positiv charge, then the H atom from HCL is taken up by -OH to form oxonium ion.
3- dehydration
water molecule is removed from oxonium ion to form another iminium ion which acts as an electrophile
4-
5- attack of nucleophile on electrophille
the nulceophile (enoliable ketone) attacks on the electrophilie (iminium ion) to form a complex unstable intermediate
6- dehydrogenation
the hydrogen atome i removed from the instable oxonium ion to form beta-amino carbonyl compound

Question 21

mannich reaction

Answer 21

reaction in which secondary amine, formaldehyde and enoiable ketone react in the presence of HCL to form beta-aminocarbonyl compound

Question 22

mannich reaction applications

Answer 22

-employed in the organic synthesis of natural compounds such peptides, nucleotides, antibodies and alkaloids.
-used in agro-chemical such as plant growth regulators, and in polymer chemistry
-used as a catalyst and main mechanism of formalin tissue cross-linking
-used as catalyst and main mechanism of formalin tissue cross-linkage
-b-amino acids are usefull intermediates for the preparation of B-lactams and B-amino acids

Question 23

Grignards reagent preparation

Answer 23

Preparation +
The grignard reagent is. prepared by the heterogenous reactions in which the reactants of different physical states are made to react with each other. The alkyl halide in a solution is made react reach with magnesiom on the surface of solid magnesion.
» The mechanism is not understood but it is certain that the first interaction is b/w magnesium and halogen atom in the presence ether which is then combined with alkyl group
= The ether solution of Grignards reagent can be used diversely used for further reaction and synthesis

Question 24

Grignard reaction

Answer 24

Grignard reagent is a highly reactive species it reacts with many organic and inorganic compounds for the synthes of many other compounds. The metals including magnesium are less electronegative than carbon and the carbon-magnesium bond in Grignard reagents, though covalent are highly polar with alkyl group having a considerable carbs ion character.
The magority of Grignards reagent fal into two main categories:
Compounds with active hydrogen
Reaction with carbonyl compounds

Question 25

Grignard’s reaction with compounds having active hydrogen

Answer 25

hydrogen which is acidic in nature is
Called “active hydrogen”
The carbanion character of the grigard’s reagent due to alkyl group makes it to react even with weak acids like water, alcohols, amines and acetylene (with active hydrogen), These reactions form alkane
-reaction with h20
-reaction with alcohol
-reaction with amine
- reaction with acetylene

Question 26

Grignard’s reaction with carbonyl compounds

Answer 26

-with aldehydes or ketones
-with esters
-with CO2
-with nitrites

Question 27

Applications of Grignard’s reagent

Answer 27

-Grignard’s reagent reaction are used for the preparation of amide acetals, amino group compounds, organo sulphur compounds, ethers, ketones, aldehydes
-it can be used for the production of several compounds that has Avery important application in the pharmaceuticals, perfumes, and specially chemical fields

Question 28

Metal hydride reaction

Answer 28

The reactions in which metal hydrides such as NaBH4, LiAlH4 and H2 catalyst are used to reduce carbonyl compounds and many of the other compounds such as carboxylic acids is known as metal hydride reduction reaction

Question 29

Metal hydride reaction for reduction of aldehydes/ketones

Answer 29

1- addition of hydrogen
in this step, the hydrogen from the LiAlH4 attacked on the carbonyl carbon of aldehyde to form anion.
2- quenching reaction
In this step, the anion takes the hydrogen from water of or HCl to form primary alcohol (ketones will give secondary alcohol)

Question 30

Metal hydride reaction for reduction of carboxylic acid

Answer 30

1- addition if hydrogen
The hydride ion from LiAlH4 attacks on the carboxylic acid to form anion
2- removal of hydroxyl group
The -OH group is removed from the anion to form aldehyde
3- addition of another hydride ion another hydride ion from LiAlH4 attacks on the aldehyde and again forms and anion
4- quenching reaction-
Anion takes hydrogen form the H-OH or HCL to form primary alcohol

Question 31

Application of metal hydride reactions

Answer 31

-The metal hydride’s are used as hydrogen storage, rechargeable bateries, hydrogen compressors , heat storage and heat pumps etc.
-They ate also used for isotope separation and powder metalurgy
-it is used as sensors and activators and also in hydrogen