Some Basic Principles and Techniques

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47. Bromine is found to be more electronegative than Carbon which leads to heterolytic fission. Due to the higher electronegativity the electrons displace from carbon to Br. Therefore, CH₃ gets positive charge and Br gets negative charge and hence option (ii) is found to be the correct one.

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Carbocation is correct since H⁺ attacks on propene and the delocalization of electrons can take place in two possible ways which can be shown as-

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45. Option (iv) is found to be the correct one since the stabilisation of carboxylate ion depends upon the dispersal of the negative charge. And the dispersal depends upon two factors, i.e., +R effect of the carboxylate ion and Inductive effect of the halogens. In all the above structures, +R effect is common, but halogen atoms are uncommon. Therefore, dispersal of negative charge depends upon the halogen atoms. Fluorine is most electronegative, in structure (iv) two F atoms are present and hence more dispersal of negative charge is there.

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44. Option (i)

is found to be the correct one since the order of electronegativity of the attached group is found to be: 

Cl > Br > C > Mg. 

Greater the electronegativity of the group attached to the C  greater will be the positive charge. Therefore, in case (i) asterisk C will have the greatest positive charge.

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43. Option (ii) 3,4- dimethyl hexane is correct since in selecting the longest continuous carbon chain both the ethyl groups are included while the third and fourth carbons have methyl groups as a substituent.

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42. Option (i) II > I > III is correct since in case (I), positively charged C is attached to two alkyl groups and is stabilized through  +I effect. In case (II), +R effect of - OCH3group stabilizes this carbocation. In case (III), - I effect of - OCH3 group destabilizes the carbocation.

Hence, the order of stability is given as: 

II > I >III.

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41. Option (ii) Partition is correct since partition chromatography is based on the principle of continuous differential partitioning of components of a mixture between a stationary and a mobile phase. Paper chromatography is a type of partition chromatography only.

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40. Option (iv)

Thin layer chromatography is correct since thin layer chromatography is a method for analysing the mixtures by separating the components of the mixture. This technique can be used to determine the number of components in a mixture, the identity of compounds and the purity of compounds by observing the appearance of a product or the disappearance of a reactant. It can also be used to analyse the progress of a reaction. 

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39. Option (iv)

Steam distillation is correct since this technique is applicable to separate the substances which are steam volatile and are immiscible with water. In steam distillation, steam from a generator is passed through a heated flask containing the liquid to be distilled. The mixture of steam and the volatile organic compound is then condensed and is collected. The compound is later separated from water using the separating funnel.

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38. Option (iii)

Alkyl halides is correct since functional isomers are the ones which have the same molecular formula but different functional groups being present in them. 

Alcohols are functional isomers of ethers while aldehydes are the functional isomers of ketones whereas cyanides are functional isomers of isocyanides.  Only alkyl halides are the ones which do not show functional isomerism.