Class XII 13.Amines [Organic Chemistry]

Introduction to Nitrogen Containing Compounds: “The chief commercial use of amines is as intermediates in the synthesis of dyes, synthetic fibres and

medicines.”

Functional groups containing nitrogen are present in a variety of naturally occurring as well as man-made

organic compounds.

These functional groups impart physicochemical characteristics to these molecules.

These groups are responsible for their unique chemical reactivity patterns and play crucial roles in the

preparation of drugs, agrochemicals, dyes and molecules of life.

There are many functional groups, which contain one or more nitrogen atoms.

Some categories of compounds based on these functional groups include nitro compounds, amines, cyanides,

isocyanides and diazo compounds.

The nitro compounds are easily obtained in the pure state. The nitro group influences the reactivity of

attached alkyl or aryl group and the functional groups present on them.

Acidic strength of phenols and reactivity of aryl halides towards nucleophilic substitution are enhanced if a

nitro group is present on their o/p positions.

In aliphatic nitro compounds, a carbanion can be generated easily and reactions performed to obtain various

products including ketones.

Amines, usually formed from nitro compounds, halides, ketones, amides, imides etc., exhibit hydrogen bonding

which influences their physical properties.

In alkyl amines, a combination of electron releasing, steric and H-bonding factors influence the stability of

their ammonium cations in protic polar media and thereby the basic nature of these amines.

In aromatic amines, electron releasing and withdrawing groups, respectively, increase and decrease their basic

character.

Amines are weak bases.

The reactions of amines are governed by the availability of the unshared pair of electrons on nitrogen and

proceed by initial attack of electrophiles and subsequent transformation to products.

The influence of the number of hydrogen at N, on the type of reactions and the nature of products is

responsible for distinguishing and separating primary, secondary and tertiary amines.

The amino and acetylamino groups enhance the reactivity of the aromatic ring towards electrophiles.

Organic cyanides are not unsafe to use and acetonitrile, the first member of the series, is a solvent of choice

for performing organic reactions.

They are usually obtained from halides, ketones, amides and diazonium salts and undergo reactions with

nucleophiles.

With Grignard reagent, they uniquely form ketones. At alpha carbon of nitriles, a carbanion is generated for

subsequent reactions with electrophiles.

Isocyanides are easily formed from halides or primary amines and undergo reactions at isocyanide carbon first

with an electrophile and then with a nucleophile.

Aryl diazonium salts, usually obtained from aromatic amines undergo replacement of the diazonium group with a

variety of nucleophiles to provide advantageous methods for forming aryl halides, cyanides, phenols and

reductive removal of amino group and thus constitute useful synthetic reagents. Coupling reactions of aryl

diazonium salts with phenols or amines form an important class of dyes.

Physical Properties Lower members of amines are gases, most of the higher members are liquids while some aromatic amines are solids.

Majority of amines have unpleasant odour.

Aromatic amines, in general, are toxic.

Most of the amines when pure are colourless but as they are easily oxidized, they get coloured due to impurities.

Amines are polar compounds and have higher boiling points than non-polar compounds such as hydrocarbons of

the same molecular mass.

All amines can form hydrogen bonds as proton acceptors, but only primary and secondary amines can donate

proton in hydrogen bonding.

Thus, primary and secondary amines, because of intermolecular hydrogen bonding, have higher boiling points

than tertiary amines.

All the three classes of amines can form hydrogen bonds with water.

Amines of low molecular mass are soluble in water but as the hydrophobic part of the amine possess more than

six carbons, their solubility in water decreases and still larger amines are essentially insoluble in water.

Because of their weaker hydrogen bonds, the solubility of amines in water is less than that of alcohols.

Amines are soluble in organic solvents like ether, benzene, alcohol, etc.

Basic Character of Amines: All classes of amines contain nitrogen atoms that bear unshared pair of electrons. The tendency of nitrogen to

share these electrons with acids is responsible for the basic character of amines which is affected by the

number and the nature of their alkyl or aryl groups.

Like ammonia, amines are strong bases and react with mineral acids to form ammonium salts from which they

can be liberated by treatment with a strong base (such as sodium hydroxide).

For comparison of the basic character of amines, the equilibrium constant of following reaction is taken as a

measure of their basic character:

;

Since [H2O] is constant, it is convenient to incorporate it into the equilibrium constant, thereby giving the

above expression for the basicity constant Kb.

All classes of aliphatic amines (Kb of about 10–3 to 10–4) are somewhat stronger bases than ammonia (Kb,1.8 × 10–5).

Aromatic amines are weaker bases (Kb~10–9) and substituents on their aromatic ring have a marked affect on

their basicity as p-Nitroaniline is only 1/4000 as basic as aniline.

Structure -Basicity Relationship of Amines:

The basic character of an amine depends on the ease of formation of its ammonium cation by accepting a

proton and is thus directly related to the stability of this cation.

So, for understanding basic character of amines in relation to their alkyl/aryl groups, we have to compare the

stabilities of the amines with the stabilities of the cations they form after protonation.

In aliphatic amines, the electron-releasing alkyl groups stabilise their ammonium cations by dispersing the

positive charge, and in parent amine make the nitrogen unshared electrons more available for sharing with a

proton.

Thus, the basic character of aliphatic amines should increase with increase of alkyl substitution. But it does not

occur in a regular manner as a secondary aliphatic amine is unexpectedly more basic than a tertiary amine in

solutions.

Basicity Order: (ET)2NH > Et2N > EtNH2 > NH3;

(Me)2 NH > MeNH2 > (Me)3N > NH3

Indeed, in gas phase, where the solvent effect is missing, the basic trend in nature is as expected i.e.

Tertiary amine > secondary amine > primary amine > ammonia.

In solution, ammonium cations are stabilized not only by electron -releasing effect of the alkyl groups but also

by solvation through their hydrogen bond with the solvent. It is evident that due to the number of hydrogen

atoms present on the nitrogen and thereby similar number of hydrogen bonds, the stability of aliphatic

ammonium cations and also the basic strength will be in the order:

Primary > secondary > tertiary,

which is opposite to the alkyl group electron-releasing effect based basic strength order. There could also be

some steric repulsion to H-bonding in cations derived from tertiary amines.

In view of these considerations, it may be concluded that it is a combination of electron-releasing, H-

bonding and steric factors that determine the stability of the ammonium cations in solution and thereby

resulting in the basic strength order of aliphatic amines as

Secondary > tertiary > primary amines.

Aromatic amines are weaker bases than ammonia and aliphatic amines.

For a structural explanation of this property, we should realize that an additional feature in the structures of

aromatic systems is their resonance stabilization.

The structure of aniline is a hybrid of five contributing species because of the conjugation of unshared

electron pair with the aromatic ring, whereas we can write only two Kekule structures for anilinium cation.

Since resonance stabilizes an aromatic amine more than it stabilizes its ammonium cation, the proton

acceptability and thereby basic strength of aromatic amines would be less.

It may also be argued that due to resonance, unshared electrons on nitrogen in aromatic amines are less

available for sharing with a proton– a feature opposite to that in alkyl amines.

An electron releasing group present in an aromatic amine ring especially in o/p position, stabilises the ammonium

cation formed after protonation of amine and hence increases the basic strength of aromatic amine.

An electronwithdrawing group adversely affects the stability of an aromatic ammonium cation and decreases

the basic strength of parent aromatic amine.

The electron releasing and withdrawing groups will also, respectively, enhance and decrease the availability of

unshared electrons on nitrogen and thereby basic strength of aromatic amines.

Separation of Primary, Secondary and Tertiary Amines The mixture of amines is reacted with benzene sulphonyl chloride and the product mixture obtained is treated

with aq. HCl and filtered.

The filtrate which contains tertiary amine as its hydrochloride is isolated as amine by additon of base.

The acid insoluble residue is treated with aq. KOH solution and filtered.

The filtrate on acidification gives the sulphonamide of primary amine which is isolated after hydrolysis.

The sulphonamide insoluble in alkali, is hydrolysed to get secondary amine.

SOME COMMERCIALLY IMPORTANT COMPOUNDS The chief commercial use of amines is as intermediates in the synthesis of dyes and synthetic fibres.

These are also used as medicines due to their physiological and psychological effects.

o Aniline: It is one of the most important of all the amines. It is manufactured by the reduction of nitrobenzene

using; iron-filings and hydrochloric acid, and catalytic hydrogenation.

;

Catalytic hydrogenation of nitro group takes place smoothly with hydrogen gas in presence of finely divided

nickel or platinum as catalyst.

N, N-Dimethylaniline (DMA): It is used as a raw material in the preparation of a number of azo dyes, for

example, methyl orange, crystal violet-malachite green, etc. It couples readily to give p-azo derivatives. DMA is

prepared by methylation of aniline with bromomethane

1,6-Hexamethylenediamine: It is used as a raw material in the production of nylone-66

Novocaine: It is also called procaine and is used as a local anaesthetic. It was developed in 1905 and contains a

primary and a tertiary amino groups.

A number of N containing compounds which act as bases occur in nature. These are known as alkaloids. In these

compounds, nitrogen may be present in the form of primary, secondary and tertiary amino group. Most of the

alkaloids produce striking physiological effect. Caffeine–a central nervous system stimulant, occurs in tea

leaves, coffee bean and cola nut, nicotine (present in tobacco plant), atropine (present in Atropa belladonna)

and cocaine (present in Erythroxylum coca) are some examples of alkaloids. In small doses, nicotine acts as a

stimulant, but in larger doses, it causes depression, nausea and vomitting. Atropine is an intense poison. In

0.5 - 1.0% concentration, it is used to dilate the pupil of the eye in ophthalmic examinations. In small doses,

cocaine decreases fatigue and increases mental activity. Prolonged use of cocaine leads to physical addiction

and to periods of deep depression.

A large number of medically and biologically important compounds are amines. A few examples are given as

follows:

Adrenaline, a hormone, is released into the blood stream when an animal senses danger. It causes an increase in

blood pressure and a widening of passages of the lungs. All these effects prepare the animal to fight or to flee.

Amphetamine is a powerful stimulant.

Dopamine is a neurotransmitter in the brain. Abnormalities in the level of dopamine cause many psychological

disorders. Dopamine also plays an important role in regulation and control of movement, motivation and cognition.

Two important nitrogen containing explosives are trinitrotoluene(TNT) and glyceryl trinitrate.

Trinitrotoluene(TNT) is prepared by treating toluene with a mixture of nitric and sulphuric acids.

Glyceryl trinitrate is an explosive component of dynamite which is prepared by treating glycerol with

concentrated nitric acid.

Hinsberg’s Test

The Hinsberg reaction is a chemical test for the detection of amines. It is an excellent test for distinguishing

primary,secondary and tertiary amines. In this test, the amine is shaken well with Hinsberg reagent in the

presence of aqueous alkali (either KOH or NaOH). A reagent containing an aqueous sodium hydroxide solution and

benzenesulfonyl chloride is added to a substrate. A primary amine will form a soluble sulfonamide salt which

precipitates after addition of diluted hydrochloric acid. A secondary amine in the same reaction will directly form

an insoluble sulfonamide. A tertiary amine will not react with the sulfonamide but is insoluble. After adding dilute

acid this insoluble amine is converted to a soluble ammonium salt. In this way the reaction can distinguish between

the three types of amine. The Hinsberg reaction was first described by Oscar Hinsberg in 1890 .

The Carbylamine reaction

The Carbylamine reaction is a chemical test for detection of primary amines. In this reaction, the analyte is heated

with alcoholic potassium hydroxide and chloroform. If a primary amine is present, the isocyanide is formed.

The carbylamine test does not give a positive reaction with secondary and tertiary amines.

Nitrous Acid Test

Procedure: : Dissolve 0.5 mL or 0.5 g of unknown in 1.5 mL of conc. HCl diluted with 2.5 mL of water, and cool the

solution to 0oC in a beaker of ice. Dissolve 0.5 g of sodium nitrite in 2.5 mL of water and add this solution dropwise,

with shaking, to the cold solution of the amine hydrochloride. Continue the addition until the mixture gives a positive

test for nitrous acid. The test is carried out by placing a drop of the solution on starch-iodide paper; a blue color

indicates the presence of nitrous acid. If the test is positive, move 2 mL of the solution to another test tube, warm

gently, and examine for evolution of gas.

Positive Test

1o aromatic amines- rapid bubbling after addition of sodium nitrite (with heating) is a positive test.

2o amines- pale yellow oil with no evolution of gas is a positive test.

3o aliphatic amines- immediate positive test for nitrous acid with no evolution of gas is a positive test.

3o aromatic amines- dark-orange solution or orange solid, when treated with base turns green is a positive test.

An azo coupling

An azo coupling is an organic reaction between a diazonium compound and another aromatic compound that produces

an azo compound. In this electrophilic aromatic substitution reaction, the aryldiazonium cation is the electrophile

and the activated arene is a nucleophile. In most cases, including the examples below, the diazonium compound is also

aromatic.

Uses of the reaction:The product will absorb longer wavelengths of light (specifically they absorb in the visible

region) than the reactants because of increased conjugation. Consequently, aromatic azo compounds tend to be

brightly colored due to the extended conjugated systems. Many are used as dyes. Important azo dyes include

methyl red and pigment red.

Class XII 13.Amines [Organic Chemistry]

Work Sheet ( WS – 13 . 1)

A. Fill in the blanks:

1. Nitrogen orbitals in amines are _______ hybridised and the geometry of amines is

pyramidal.

2. Amines are classified as ____________, _____________ and ___________ depending

upon the number of hydrogen atoms replaced by alkyl or aryl groups in

ammonia molecule.

3. H2N–CH2–CH2–NH2 is named as _____________________________________.

4. C6H5NH2 is the simplest example of arylamine. In common system, it is known as

_____________.

5. Nitro compounds are reduced to ___________ by passing hydrogen gas in the

presence of finely divided nickel, palladium or platinum and also by reduction

with metals in acidic medium.

6. The process of cleavage of the C–X bond by ammonia molecule is known as

_______________.

7. _______________ on reduction with lithium aluminium hydride (LiAlH 4 ) or catalytic

hydrogenation produce primary amines. This reaction is used for ascent of

amine series.

8. Gabriel synthesis is used for the preparation of____________ amines.

9. The amide which gives propanamine by Hoffmann bromamide reaction is

___________________.

10. The lower aliphatic amines are gases with __________ odour.

11. The amine produced by the Hoffmann degradation of benzamide is _______________.

12. Lower aliphatic amines are soluble in water because they can form ________________

bonds with water molecules.

13. ______________ amines do not have intermolecular association due to the absence

of hydrogen atom available for hydrogen bond formation.

14. Amines, being ____________ in nature, react with _____________ to form salts.

15. Amine salts are ___________ in water but ____________ in organic solvents like

ether.

16. Larger the value of Kb or smaller the value of pKb, _________________ is the base.

17. Aromatic amines are _____________ bases than ammonia due to the electron

withdrawing nature of the aryl group.

18. In case of substituted aniline, it is observed that electron releasing groups like –

OCH3, –CH3 _____________basic strength whereas electron withdrawing groups like –

NO2, –SO3, –COOH, –X _______________ it.

19. Aliphatic and aromatic __________ amines on heating with chloroform and

ethanolic potassium hydroxide form isocyanides or carbylamines which are foul

smelling substances.

20. Aniline reacts with bromine water at room temperature to give a white precipitate

of 2,4,6-tribromoaniline.

Class XII 13.Amines [Organic Chemistry]

Class Assignment ( CA – 13. 1) : NCERT Solved examples 13.1 to 13.5 + Intext Questions 13.1 to 13.9 NCERT Solved examples 13.1 to 13.5. Example 13.1 Write chemical equations for the following reactions: (i) Reaction of ethanolic NH3 with C2H5Cl. (ii) Ammonolysis of benzyl chloride and reaction of amine so formed with two moles of CH3Cl. Example 13.2 Write chemical equations for the following conversions: (i) CH3–CH2–Cl into CH3–CH2–CH2–NH2 (ii) C6H5–CH2–Cl into C6H5–CH2–CH2–NH2

Example 13.3 Write structures and IUPAC names of (i) the amide which gives propanamine by Hoffmann bromamide reaction. (ii) the amine produced by the Hoffmann degradation of benzamide. Example 13.4 Arrange the following in decreasing order of their basic strength: C6H5NH2, C2H5NH2, (C2H5)2NH, NH3.

Example 13.5 How will you convert 4-Nitrotoluene to 2-Bromobenzoic acid ?

+ Intext Questions 13.1 to 13.9

13.2 (i) Write structures of different isomeric amines corresponding to the molecular formula, C4H11N. (ii) Write IUPAC names of all the isomers. (iii) What type of isomerism is exhibited by different pairs of amines? 13.3 How will you convert : (i) Benzene into aniline ; (ii) Benzene into N, N-dimethylaniline ; (iii) Cl–(CH2)4 –Cl into hexan-1,6-diamine? 13.4 Arrange the following in increasing order of their basic strength:

(i) C2H5NH2, C6H5NH2, NH3, C6H5CH2NH2 and (C2H5)2NH ; (ii) C2H5NH2, (C2H5)2NH, (C2H5)3N, C6H5NH2 ; (iii) CH3NH2, (CH3)2NH, (CH3)3N, C6H5NH2, C6H5CH2NH2.

13.5 Complete the following acid-base reactions and name the products:

(i) CH3CH2CH2NH2 + HCl (ii) (C2H5)3N + HCl 13.6 Write reactions of the final alkylation product of aniline with excess of methyl iodide in the presence of sodium

carbonate solution. 13.7 Write chemical reaction of aniline with benzoyl chloride and write the name of the product obtained. 13.8 Write structures of different isomers corresponding to the molecular formula, C3H9N. Write IUPAC names of the

isomers which will liberate nitrogen gas on treatment with nitrous acid. 13.9 Convert : (i) 3-Methylaniline into 3-nitrotoluene. (ii) Aniline into 1,3,5 - tribromobenzene.

Class XII 13.Amines [Organic Chemistry]

Home Assignment ( HA –– 13.1) : NCERT EXERCISE Question number 13.2 to 13.5 ; 13.8, 13.9 & 13.11. 13.2 Give one chemical test to distinguish between the following pairs of compounds. (i) Methylamine and dimethylamine ; (ii) Secondary and tertiary amines ; (iii) Ethylamine and aniline ; (iv) Aniline

and benzylamine ; (v) Aniline and N-methylaniline. 13.3 Account for the following: (i) pKb of aniline is more than that of methylamine. (ii) Ethylamine is soluble in water whereas aniline is not. (iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide. (iv) Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration

gives a substantial amount of m-nitroaniline. (v) Aniline does not undergo Friedel-Crafts reaction. (vi) Diazonium salts of aromatic amines are more stable than those of aliphatic amines. (vii) Gabriel phthalimide synthesis is preferred for synthesising primary amines. 13.4 Arrange the following: (i) In decreasing order of the pKb values: C2H5NH2, C6H5NHCH3, (C2H5)2NH and C6H5NH2 ; (ii) In increasing order of basic strength: C6H5NH2, C6H5N(CH3)2, (C2H5)2NH and CH3NH2 ; (iii) In increasing order of basic strength: (a) Aniline, p-nitroaniline and p-toluidine ; (b) C6H5NH2, C6H5NHCH3, C6H5CH2NH2. (iv) In decreasing order of basic strength in gas phase: C2H5NH2, (C2H5)2NH, (C2H5)3N and NH3 ; (v) In increasing order of boiling point: C2H5OH, (CH3)2NH, C2H5NH2 ; (vi) In increasing order of solubility in water: C6H5NH2, (C2H5)2NH, C2H5NH2. 13.5 How will you convert: (i) Ethanoic acid into methanamine ; (ii) Hexanenitrile into 1-aminopentane ; (iii) Methanol to ethanoic acid ; (iv) Ethanamine into methanamine ; (v) Ethanoic acid into propanoic acid ; (vi) Methanamine into ethanamine ; (vii) Nitromethane into dimethylamine ; (viii) Propanoic acid into ethanoic acid? 13.8 Accomplish the following conversions: (i) Nitrobenzene to benzoic acid ; (ii) Benzene to m-bromophenol ; (iii) Benzoic acid to aniline ; (iv) Aniline to 2,4,6-tribromofluorobenzene ; (v) Benzyl chloride to 2-phenylethanamine ;(vi) Chlorobenzene to p-chloroaniline ; (vii) Aniline to p-bromoaniline ; (viii) Benzamide to toluene ;(ix) Aniline to benzyl alcohol.

Class XII 13.Amines [Organic Chemistry] Special Assignment ( SA –– 13.1)

1. Why is acetyl chloride more easily hydrolyzed than chloride more easily hydrolysed than benzoyl chloride?

2. Why are amides less basic than amines?

3. Why it is difficult to prepare pure amines by the ammonolysis of alkyl halides?

4. Why is tert – butyl amine not prepared by the action of NH3 on tert-butyl bromide?

5. Why is aniline not prepared by Gabriel phthalimide reaction?

6. Why do quaternary ammonium salts having four different groups attached to N show optical activity?

7. Why is the C-N bond in aromatic amines shorter than that in aliphatic amines?

8. Why are amines polar compounds?

9. Why is the boiling point of ethylamines lower than ethanol?

10. Why are amines soluble in water and alcohols?

11. Why 2 amines are more basic than 3 and 1 amines?

12. Why the order of basicity of amines (1, 2 and 3) different in vapour phase than in aqueous phase?

13. Why are amines basic in nature?

14. Aniline is a weaker base than cyclohexane. Why?

15. Account for the following:-

(i) p- Nitroaniline is a weaker base than aniline. (ii) p- Methoxyaniline is a stronger base than aniline.

16. Give reason: Reaction of an alkyl halide with AgNO2 forms nitroalkane as the major product but

with NaNO2, alkyl nitrite is the major product.

17. If – NO2 or – COOH group is attached to carbon atom of the benzene ring, electrophilic substitution becomes

difficult. Why?

18. Of benzene and toluene, which is more easily nitrated and why?

19. Boiling point of nitroalkalene are higher than their corresponding alkyl nitrites/ alkanes. Why?

20. Why does 1 and 2 nitro compounds reacts with bases to form carbanion salts?

21. Why is alpha hydrogen atom in aliphatic nitro compounds acidic?

22. Why does nitrobenzene not undergo friedel-craft reaction?

23. Explain why is nucleophillic substitution of p-nitro chloro benzene easier than that of chlorobenzene?

24. Arrange the following in order of decreasing basic strength:

(a) Ethyl amine, Ammonia, Triethyl amine

(b) Aniline, p- Nitroaniline , p- Toluidine

25. Amine group in aniline is ortho and para directing. Why does then aniline on nitration give substantial amount of

m-nitroaniline

26. Primary amines have higher boiling points than tertiary amines. Why?

27. ‘Amide are more acidic than amines’. Why?

28. Arrange the following amines in the ascending order of basic strength giving reason-

EtNH2, Et2NH, Et3N, in aqueous solution?

29. Explain the role of mineral acid in the reaction of a carbonyl compound with KCN (aq)?

30. Why is acetonitrile preferred as a solvent for running organic reaction?

31. Why aniline is acetylated first to prepare mono bromo derivative?

32. Ammonolysis of alkyl halide does not give a corresponding amine in pure state. Explain?

33. Explain why methyl bromide reacts with KCN go give mostly methyl cyanide but it reacts with AgCN to give

mostly methyl isocyanide.

34. Why is necessary to maintain the temperature between 273 K and 278 K during diazotization?

35. Why does silver chloride dissolve in aqueous methyl amine solution?

36. How can the following conversion be carried out :-

(a) p-toluidine to 2- bromo-4- methylanline; (b) Aniline to iodobenzene ; (c) Aniline to benzonitrile.

Class XII Chemistry Unit-14. Biomolecules

Topic - 14.1 Carbohydrates

Work Sheet ( WS – 14 . 1) B. Fill in the blanks:

1. The carbohydrates may be defined as ____________ _________ polyhydroxy aldehydes or

ketones or the compounds which produce such units on ______________ .

2. Some of the carbohydrates, which are sweet in taste, are also called _________.

3. The most common sugar, used in our homes is named as _____________whereas the sugar

present in milk is known as ________________

4. Carbohydrates are also called _________________ (Greek: sakcharon means sugar).

5. A carbohydrate that cannot be hydrolysed further to give simpler unit of polyhydroxy

aldehyde or ketone is called a _____________________.

6. Carbohydrates that yield two to ten monosaccharide units, on hydrolysis, are called

______________________.

7. Carbohydrates which yield a large number of monosaccharide units on hydrolysis are

called _____________________.

8. All those carbohydrates which reduce Fehling’s solution and Tollens’ reagent are referred

to as___________________ sugars.

9. All monosaccharides whether aldose or ketose are ______________ sugars.

10. If a monosaccharide contains an aldehyde group, it is known as an ___________ and if it

contains a keto group, it is known as a _____________.

11. If ________________ is boiled with dilute HCl or H2SO4 in alcoholic solution, glucose and

fructose are obtained in equal amounts.

12. _____________ is obtained by hydrolysis of starch by boiling it with dilute H2SO4 at 393 K under

pressure.

13. On prolonged heating with HI, ______________ forms n-hexane, suggesting that all the six

carbon atoms are linked in a straight chain.

14. Glucose reacts with hydroxylamine to form an _____________and adds a molecule of

hydrogen cyanide to give _________________.

15. Glucose gets oxidised to six carbon carboxylic acid ,_____________ acid on reaction with a

mild oxidising agent like bromine water.

16. Acetylation of glucose with acetic anhydride gives glucose pentaacetate which confirms

the presence of _______________ groups.

17. The two cyclic hemiacetal forms of glucose differ only in the configuration of the hydroxyl

group at C1, called _____________ carbon (the aldehyde carbon before cyclisation). Such

isomers, i.e., α-form and β-form, are called _____________.

18. One of the common disaccharides is sucrose which on hydrolysis gives equimolar mixture

of D-(+)-___________ and D-(-) ____________.

19. The carbohydrates are stored in animal body as _________________. 20. ________________ is a predominant constituent of cell wall of plant cells.

Class XII Chemistry Unit-14. Biomolecules

Topic - 14.1 Carbohydrates

Class Assignment ( CA – 14. 1) : NCERT Intext Questions 14.1 to 14.3:

14.1 Glucose and sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds)

are insoluble in water. Explain.

14.2 What are the expected products of hydrolysis of lactose?

14.3 How do you explain the absence of aldehyde group in the pentaacetate of D-glucose?

Topic - 14.2 Proteins, Fats & Nucleic Acids

Class Assignment ( CA – 14. 2) : NCERT Intext Questions 14.4 to 14.8:

14.4 The melting points and solubility in water of amino acids are generally higher than that of the corresponding

halo acids. Explain.

14.5 Where does the water present in the egg go after boiling the egg?

14.6 Why cannot vitamin C be stored in our body?

14.7 What products would be formed when a nucleotide from DNA containing thymine is hydrolysed?

14.8 When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What

does this fact suggest about the structure of RNA?

Class-XII Chemistry [ Special Assignment 14.1 ] Unit-14. Biomolecules

1. How many chiral centres are there in D-(-)-Fructose?

2. How many chiral centres are there in D-(-)-Glucose?

3. Where does the water present in the egg go after boiling the egg?

4. Why do monosaccharides form cyclic structures? Give cyclic structure of glucose.

5. Name the amino acids obtained when tripeptide (Gly-Ala-Leu) is hydrolysed.

6. Explain how curdling of milk occurs. What structural changes take place?

7. Discuss the primary, secondary & tertiary structure of proteins. What is the effect on these structure of

denaturation?

8. Drugs which are proteins such as insulin cannot be taken by mouth but must be injected. Why?

9. Amino acids show amphoteric behavior. Explain with suitable diagram.

10. In alkaline solution, an amino acid contains 2 basic groups – NH2 and –COO-, which is more basic? If acid is

added to the solution, what will happen?

11. When RNA is hydrolyzed there is no relationship among the quantities of four bases obtained unlike DNA.

What does this fact indicate about the structure of RNA?

12. If three amino acids viz., glycine, alanine and phenylalanine react together, how many possible tripeptides can

be formed? Write down the names of each one. Also write their names using three and one letter

abbreviations for each amino acid.

13. Write down the structures and names of the products obtained when D-glucose is treated with

i) HCN , ii) Excess of C6H5NHNH2 , iii) (CH3CO)2O & iv) Br2 water.

14. An unsaturated fatty acid having formula C17H33COOH has a double bond at C-9. Amongst two stereoisomers

of the acids i.e. cis and trans, which do you expect to have higher m.p.? Explain why?

15. Give reasons for the following:

(i) Amino acids have relatively higher melting point as compared to corresponding halo acids

(ii) Amino acids are amphoteric in behaviour

(iii) On electrolysis in acidic solution amino acids migrate towards cathode while in

alkaline solution these migrate towards anode ; &

(iv) the monoamino monocarboxylic acids have two pK values.

Class XII Chemistry Unit-14. Biomolecules Topic - 14.2 Proteins, Fats & Nucleic Acids

Work Sheet (WS – 14 . 2) A. Fill in the blanks:

1. All proteins are polymers of ___________________ acids.

2. Chief sources of ______________ are milk, cheese, pulses, peanuts, fish, meat, etc.

3. Amino acids are classified as ___________, ___________ or

____________depending upon the relative number of amino and carboxyl groups in

their molecule.

4. Equal number of amino and carboxyl groups makes Amino acid _______________.

5. More number of amino than carboxyl groups makes Amino acid ___________ and more

carboxyl groups as compared to amino groups makes ___________.

6. The amino acids, which can be synthesised in the body, are known as ___________

__________________ amino acids.

7. In zwitter ionic form, amino acids show _______________ behaviour as they react

both with acids and bases.

8. Except ____________ , all other naturally occurring α-amino acids are optically active,

since the -carbon atom is asymmetric.

9. Proteins are the polymers of -amino acids and they are connected to each other by

_____________ bond or ____________ linkage.

10. When carboxyl group of glycine combines with the amino group of alanine we get a

dipeptide, _________________________.

11. Any change in this _______________ structure i.e., the sequence of amino acids

creates a different protein.

12. Protein found in a biological system with a unique three-dimensional structure and

biological activity is called a _____________ protein.

13. During denaturation ________and _________ structures are destroyed but

_________ structure remains intact.

14. The melting points and solubility in water of amino acids are generally ____________

than that of the corresponding halo acids.

15. Almost all the enzymes are _______________ proteins.

16. Enzymes are very ____________ for a particular reaction and for a particular

substrate.

17. Organic compounds required in the diet in small amounts to perform specific biological

functions for normal maintenance of optimum growth and health of the organism, are

called _____________.

18. DNA contains four bases viz. adenine (A), guanine (G), cytosine (C) and _________( ).

19. RNA molecules are of three types , named as _____________RNA (m-RNA),

__________ RNA (r-RNA) and ______________RNA (t-RNA).

20. DNA contains a five carbon sugar molecule called _________________ whereas RNA

contains _______________.

Home Assignment ( HA – 14.1) : Topic - 14.1 Carbohydrates

NCERT EXERCISE Question number 14.5 to 14.9.

14.5 What do you understand by the term glycosidic linkage?

14.6 What is glycogen? How is it different from starch?

14.7 What are the hydrolysis products of

(i) sucrose and (ii) lactose?

14.8 What is the basic structural difference between starch and cellulose?

14.9 What happens when D-glucose is treated with the following reagents?

(i) HI ; (ii) Bromine water ; & (iii) HNO3 .

Home Assignment ( HA – 14.2) : Topic - 14.2 Proteins, Fats & Nucleic Acids

NCERT EXERCISE Question number 14.12, 14.14 , 14.15 , 14.18 to 14.21 & 14.23 to 14.25.

14.12 Define the following as related to proteins :

(i) Peptide linkage (ii) Primary structure (iii) Denaturation.

14.14 What type of bonding helps in stabilising the α-helix structure of proteins?

14.15 Differentiate between globular and fibrous proteins.

14.18 What is the effect of denaturation on the structure of proteins?

14.19 How are vitamins classified? Name the vitamin responsible for the coagulation of blood.

14.20 Why are vitamin A and vitamin C essential to us? Give their important sources.

14.21 What are nucleic acids? Mention their two important functions.

14.23 The two strands in DNA are not identical but are complementary. Explain.

14.24 Write the important structural and functional differences between DNA and RNA.

14.25 What are the different types of RNA found in the cell?

Class-XII Chemistry [ Special Assignment 14.2 ] Unit-14. Biomolecules

1. Sucrose is dextrorotary. Its structure is given as:

a) What happens when sucrose solution is treated with Tollen’s reagent and why?

b) Its aqueous solution exhibits a change in rotation. Why?

2. The melting points and solubility in water of amino acids are generally higher than that of corresponding lab

acids. Explain.

3. Activation energy for acid hydrolysis of sucrose is 6.22 kJ mol-1 while it is only 2.15 kJ mol-1 when hydrolysed

by enzyme sucrose.

a) Write the mechanism of the enzyme catalysed reaction.

b) Also depict the progress of reaction against energy in both cases, diagrammatically.

4. When DNA is hydrolysed, there is a definite relation among the quantities of different bases obtained. But for

hydrolysis of RNA, it is not so. What does this suggest about the structure of DNA and RNA?

5. Identify and explain the various forces which stabilize protein structure.

6. Starch forms an emulsion rather than solution with water. Explain.

7. In a quite acidic solution, the amino acid contains two acidic groups- NH3 and -COOH , which is more acidic? If

a base is added to the solution, what will happen?

8. Comment on the cyclic & acyclic structure of glucose with supportive reactions.

9. What is the melting temperature (Tm) of DNA? A DNA molecule with more number of GC base pairs than AT

base pairs has higher Tm than the one with lesser number of GC base pairs than AT base pairs. Explain why?

10. How does DNA replicate? Give the mechanism of replication. How is the process responsible for preservation

of heredity?

Class XII Chemistry Topic - 15.1 Polymers Unit-15. Polymers

Work Sheet ( WS – 15 . 1)

A. Fill in the blanks:

1. Free radical polymerization is involved in case of _____________ polymerization.

2. In free radical polymerization, CCl4 acts as __________________agent.

3. _____________ is an example of inhibitor in free radical polymerization.

4. Two modes of polymerization of conjugated diene are _________ & __________

polymerization.

5. Acrylonitrile will undergo ______________ polymerization.

6. Propylene will undergo ______________ polymerization.

7. Step growth polymerization is involved in ______________ polymerization.

8. The starting material of PCTFE is _____________________________________.

9. In Buna – S, S stands for ______________.

10. The monomer unit of PMMA is _______________________________________.

11. The monomer unit of PAN is ________________________________________.

12. The monomer unit of PVC is _______________________________.

13. Nylon -6 is a polymer of_________________________________________.

14. Phenol formaldehyde resin is commonly called________________.

15. Natural rubber is a polymer of _______________.

16. __________________ is an example of synthetic rubber.

17. Cross linking of S-S is involved in ______________ rubber.

18. Neoprene is a _______________ ( natural/ synthetic/semi-synthetic) rubber.

19. Cotton is an example of _______________ ( natural/ synthetic/semi-synthetic)

polymer.

20. Buna-S is a _________________ (Copolymer/homopolymer).

Class XII Chemistry Unit-15. Polymers

Topic - 15.1 Polymers

Class Assignment ( CA – 15. 1) : NCERT solved example 15.1 + NCERT Intext Questions 15.1 to 15. 6 :

NCERT Intext Questions 15.1 to 15.6 : 15.1 What are polymers ? 15.2 How are polymers classified on the basis of structure? 15.3 Write the names of monomers of the following polymers:

15.4 Classify the following as addition and condensation polymers: Terylene, Bakelite, Polyvinyl chloride, Polythene. 15.5 Explain the difference between Buna-N and Buna-S. 15.6 Arrange the following polymers in increasing order of their intermolecular forces. (i) Nylon 6,6, Buna-S, Polythene. (ii) Nylon 6, Neoprene, Polyvinyl chloride.

NCERT EXERCISE Question number 15.1 to 15.11.

15.1 Explain the terms polymer and monomer.

15.2 What are natural and synthetic polymers? Give two examples of each type.

15.3 Distinguish between the terms homopolymer and copolymer and give an example of each.

15.4 How do you explain the functionality of a monomer?

15.5 Define the term polymerisation.

15.6 Is ( -NH-CHR-CO- )n, a homopolymer or copolymer?

15.7 In which classes, the polymers are classified on the basis of molecular forces?

15.8 How can you differentiate between addition and condensation polymerisation?

15.9 Explain the term copolymerization and give two examples.

15.10 Write the free radical mechanism for the polymerisation of ethene.

15.11 Define thermoplastics and thermosetting polymers with two examples of each.

Home Assignment ( HA – 15.1) :

NCERT EXERCISE Question number 14.5 to 14.9. Question -1. Make a table with the columns : S.No. ; Polymer ; Monomer ; Repeating Unit ; & Uses of polymer.

S.No. Polymer’s Name Monomer(s) Repeating Unit Type(s) of Polymer Uses of Polymer

[ Note: Table includes answers of most of the NCERT Exercise Questions]

Class XII Chemistry Unit- 16.Chemistry In Everyday Life

Topic - 16.1 Chemistry In Everyday Life Work Sheet ( WS – 16 . 1) A. Fill in the blanks: 1. Drugs compete with the natural substrate for their attachment on the active sites of

enzymes. Such drugs are called ________________ _______________.

2. Some drugs do not bind to the enzyme’s active site. These bind to a different site of

enzyme which is called ________________ site.

3. If the bond formed between an enzyme and an inhibitor is a strong covalent bond and

cannot be broken easily, then the enzyme is blocked __________________.

4. Drugs that bind to the receptor site and inhibit its natural function are called

__________________.

5. ___________________reduce or abolish pain without causing impairment of consciousness,

mental confusion, in coordination or paralysis or some other disturbances of nervous

system.

6. Because of its anti blood clotting action, _____________ finds use in prevention of heart

attacks.

7. A/an __________________tends to destroy/prevent development or inhibit the pathogenic

action of microbes such as bacteria (antibacterial drugs), fungi (antifungal agents), virus

(antiviral agents), or other parasites (antiparasitic drugs) selectively.

8. A/an __________________now refers to a substance produced wholly or partly by chemical

synthesis, which in low concentrations inhibits the growth or destroys microorganisms by

intervening in their metabolic processes.

9. Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria

are said to be ______________ spectrum antibiotics.

10. ___________________ are applied to the living tissues such as wounds, cuts, ulcers and

diseased skin surfaces.

11. 0.2 per cent solution of phenol is a/an _______________ while its one percent solution is

____________________.

12. _______________ is the most successful and widely used artificial sweetener. It is roughly 100

times as sweet as cane sugar.

13. Soaps containing sodium salts are formed by heating fat ( i.e., glyceryl ester of fatty acid)

with aqueous sodium hydroxide solution. This reaction is known as ___________.

14. Synthetic detergents are mainly classified into three categories:__________________,

__________________&__________________.

15. __________________ detergents are quarternary ammonium salts of amines with acetates,

chlorides or bromides as anions.

16. A ______________ is a chemical agent, which affects human metabolism and provides

cure from ailment.

17. Artificial ___________________ are used by those who need to check the calorie intake or

are diabetic and want to avoid taking sucrose.

18. __________________ are much in vogue and get preference over soaps because they work

even in hard water.

19. Detergents with straight chain of hydrocarbons are preferred over branched chain as the

latter are ____________________ and consequently cause environmental pollution.

20. _______________ detergents are sodium salts of sulphonated long chain alcohols or

hydrocarbons.

Class XII Chemistry Unit- 16.Chemistry In Everyday Life

Topic - 16.1 Chemistry In Everyday Life

Class Assignment ( CA – 16. 1) :

NCERT Intext Questions 16.1 to 16. 5 :

16.1 Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not

advisable to take its doses without consultation with the doctor. Why ?

16.2 With reference to which classification has the statement, “ranitidine is an antacid” been given?

16.3 Why do we require artificial sweetening agents ?

16.4 Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate.

Structural formulae of these compounds are given below.

(i) (C15H31COO)3C3H5 – Glyceryl palmitate;

(ii) (C17H32COO)3C3H5 – Glyceryl oleate.

16.5 Following type of non-ionic detergents are present in liquid detergents, emulsifying agents and

wetting agents. Label the hydrophilic and hydrophobic parts in the molecule. Identify the functional

group(s) present in the molecule.

Home Assignment ( HA –– 16.1) :

NCERT EXERCISE Question number 16.6 to 16.8; 16.11 to 16.13; 16.19 ; 16.21; 16.24 to 16.25.

16.6 Which forces are involved in holding the drugs to the active site of enzymes ?

16.7 While antacids and antiallergic drugs interfere with the function of histamines, why do these not

interfere with the function of each other ?

16.8 Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this

problem ? Name two drugs.

16.11 Why are cimetidine and ranitidine better antacids than sodium hydrogencarbonate or magnesium or

aluminium hydroxide ?

16.12 Name a substance which can be used as an antiseptic as well as disinfectant.

16.13 What are the main constituents of dettol ?

16.19 What problem arises in using alitame as artificial sweetener ?

16.21 Explain the following terms with suitable examples

(i) cationic detergents ;(ii) anionic detergents and (iii) non-ionic detergents.

16.24 Can you use soaps and synthetic detergents to check the hardness of water ?

16.25 Explain the cleansing action of soaps.