5 Marks Questions

Question 15 Marks

Attempt any five of the following:
(a) What is the structural feature characterising reducing sugars?
(b) What type of linkage is present in polysaccharides?
(c) Give examples of fat soluble vitamins.
(d) The two strands in DNA are not identical but are complementary. Explain.
(e) Write uses of B-Complex.
(f) Name the disaccharide which on hydrolysis gives two molecules of glucose.
(g) Name purines present in DNA?

Answer

Attempt any five of the following:
(i) The reducing sugars have free aldehydic or ketonic groups.
(ii) Glycosidic linkage
(iii)Fat soluble vitamins are absorbed along with fats in the diet and are stored in body's fatty tissue and in the liver. Vitamin A, D, E and K are fat soluble vitamins.
iv)In the helical structure of DNA, the two strands are held together by hydrogen bonds between specific pairs of bases. Cytosine forms hydrogen bond with guanine, while adenine forms hydrogen bond with thymine. As a result, the two strands are complementary to each other.
(v) It is required for making red blood cells, muscles.
(vi)The disaccharide which gives two molecules of glucose on hydrolysis is maltose.
(vii)Adenine and guanine

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Question 25 Marks

$(i). $Illustrate the following reactions giving suitable example in each case:
$a.$ Ammonolysis
$b.$ Coupling reaction
$c.$ Acetylation of amines
$(ii).$ Describe Hinsberg method for the identification of primary, secondary and tertiary amines. Also, write the chemical equations of the reactions involved.

Answer

$(1)$
$(a).$ Ammonolysis The process of cleavage of the $C-X$ bond by ammonia molecule is known as ammonolysis. In this process, an alkyl or benzyl halide on reaction with an ethanolic solution of ammonia undergoes nucleophilic substitution reaction in which halogen atom is replaced by an amino $(-NH_2)$ group. 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 further quaternary salts.

$(b).$ Coupling reaction Arenediazonium salts react with highly reactive $($i.e. electron$-$rich$)$ aromatic compounds such as aniline, phenols to form brightly coloured azo compounds, $\ce{Ar-N =N-Ar.}$ This reaction is called coupling reaction. e.g. Benzene diazonium chloride reacts with aniline in faintly acidic medium $(pH 4-5)$ at $273-278K,$ in which the molecule at its para$-$position is coupled with the diazonium salt to form $p-$aminoazobenzene. This is an example of coupling reaction.

$(c). $Acetylation of amines The process of introducing an acetyl group

into the molecule is called acetylation of amines.

$(2)$ The reaction of primary and secondary amines with benzenesulphonyl chloride $\ce{(C_6H_5SO_2Cl,}$ known as Hinsberg's reagent to form sulphonamides is known as Hinsberg's method $($or reaction$)$. This method $($or reaction$)$ is used for separating $1^\circ , 2^\circ$ and $3^\circ$ amines.
$(a).$ The reaction of benzenesulphonyl chloride with primary amine yields $N-$ethylbenzenesulphonamide.

The hydrogen attached to $N-$atom in sulphonamide is strogly acidic due to the presence of strong electron withdrawing sulphonyl group. Hence, it is soluble in alkali.
$(b).$ In the reaction with secondary amine$, N, N-$diethylbenzenes amide is formed.

Since, $N, N-$diethylbenzenesulphonamide does not contain any hydrogen atom attached to nitrogen atom, it is not acidic and hence, insoluble in alkali.
$c.$ Tertiary amines do not react with benzenesulphonyl chloride. as it doesn't contain replaceable hydrogens.

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Question 35 Marks

(i). Write the structures of main products when benzene diazonium chloride $\left( C _6 H _5 N_2^{+} Cl ^{-}\right)$ reacts with the following reagents.
a. $HBF _4 / \Delta$
b. $Cu / HBr$
(ii). Write the structures of A, B and C in the following reactions:
a. $C _6 H _5 NO _2 \xrightarrow{ Sn / HCl } A \xrightarrow[\Delta]{ NaNO _2+ HCl } B \xrightarrow{273 K} H$
b. $CH _3 Cl \xrightarrow{ KCN } A \xrightarrow{ LiAlH _4} B \xrightarrow[273 K]{\stackrel{273 K}{ HNO }{ }_2} C$

Answer

(1)

(2)

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Question 45 Marks

Using Valence bond theory, explain the following in relation to the paramagnetic complex $[Mn(CN)_6]^{3-}$
$a.$ type of hybridisation
$b.$ magnetic moment value
$c.$ type of complex $-$ inner, outer orbital complex

Answer

$a.$ Type of hybridisation $- d^2sp^3$
$b.$ Magnetic moment value
$=\sqrt{n(n+2)}=\sqrt{2(2+2)}=2.87 BM$
$(n =$ no. of unpaired electrons$) $
$c.$ Type of complex $-$ inner orbital

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Question 55 Marks

Write the $\text{IUPAC}$ names of the following coordination compounds:
$a.\ \left[ Pt \left( NH _3\right)_2 Cl \left( NO _2\right]\right.$
$b.\ K _3\left[ Cr \left( C _2 O _4\right)_3\right]$
$c.\ \left[ CoCl _2( en )_2\right] Cl$
$d.\ \left[ Co \left( NH _3\right)_5\left( CO _3\right)\right] Cl$
$e.\ Hg \left[ Co ( SCN )_4\right]$

Answer

$a.$ The $\text{IUPAC}$ name of $[Pt (NH_3)_2 Cl(NO_2]$ is Diamminechloridonitrito$-N-$platinum$(II).$
$b.$ The $\text{IUPAC}$ name of $K_3 [Cr (C_2O_4)_3]$ is Potassium trioxalatochromate$(III).$
$c.$ The $\text{IUPAC}$ name of $[CoCl_2 (en)_2]Cl$ is Dichloridobis $($ethane$-1,2-$diamine$)$cobalt $(III)$ chloride.
$d.$ The $\text{IUPAC}$ name of $[Co(NH_3)_5 (CO_3)]Cl$ is Pentaamminecarbonatocobalt $(III)$ chloride.
$e.$ The $\text{IUPAC}$ name of $Hg [Co (SCN)_4]$ is Mercury $(I)$ tetrathiocyanatocobaltate $(III).$

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