Important Talent Search Exams
|Allen TALLENTEX 2018 (Class 5 to 11)|
|Aakash ANTHE 2017 : 100% Scholarship (Class 8, 9, 10)|
Prob 1. The correct order of reactivity towards nucleophilic addition reaction will be
Sol. Aldehydes are more reactive than ketones due to lesser number of +I group & again the reactivity of carbonyl group depends on the major nature of alkyl group attached to it.
So correct order is
Prob 2. Which of the following will not give aldol condensation?
(A) RCH2CHO (B) RCOCH2R
(C) C6H5CHO (D) C6H5CH2CHO
Sol. Aldol condensation is given by those carbonyl compounds, which possess at least one a – H.
(C) is not having a hydrogen hence it will not give aldol condensation
Prob 3. Aldehydes & ketones can be reduced to corresponding hydrocarbons by
(A) refluxing with strong acids
(B) passing the vapours under heated PbO2
(C) Refluxing with zinc amalgam
(D) Refluxing with strong alkali
Prob 8. Arrange the following compounds in order of their decreasing activity towards Tollen’s reagent:
HCHO CH3CHO CH3COCH3 C6H5CHO
I II III IV
(A) I > II > IV > III (B) I > II > III > IV
(C) II > I > III > IV (D) none
Sol. Aldehydes are more reactive than ketones
Prob 9. The most reactive compound towards formation of cyanohydrin on treatment with KCN followed by acidification is
(A) benzaldehyde (B) p – nitrobenzaldehyde
(C) phenylacetaldehyde (D) p – hydroxybenzaldehyde
Sol. Presence of electron withdrawing group in para position increases nucleophilic addition.
Prob 10. Which of the following chemical system has most acidic hydrogen?
(A) 3 – hexanone (B) 2, 4 – hexanedione
(C) 2, 5 – hexanedione (D) 2, 3 – hexanedione
Sol. 2, 4 – hexanedione has ¾CH2¾ group surrounded on both sides of electronegative (>C=O) group, hence it is acidic in nature, the carbanions
Prob 12. Acetophenone can be prepared by
(I) Oxidation of 1 – phenylethanol
(II) Reduction of benzaldehyde with methyl magnesium bromide
(III) Friedel – crafts reaction of benzene with acetylchloride
(IV) Distillation of calcium benzoate
Which of above is correct?
(A) I & III (B) II & IV
(C) III & IV (D) I & II
Prob 13. An organic compound ‘A’ has the molecular formula C3H6O. It undergoes iodoform test. When saturated with HCl it gives ‘B’ of molecular formula C9H14O, ‘A’ & ‘B’ respectively are
(A) propanal & mesitylene
(B) propanone & mesityl oxide
(C) propanone & 2, 6 – dimethyl – 2, 5 – heptadien – 4 – one
(D) propane & meistylene oxide
Sol. Since the compound A has the molecular formula C3H6O & undergoes iodoform test, it should be CH3COCH3. Further reaction of B with HCl gives C9H14O, this should be trimer of acetone, i.e. It should be phorone.
Prob 14. What will be the product when 2-Butenal reacts with sodiumborohydride?
(A) Butanal (B) Butanol
(C) But-2-ene-1-ol (D) None
Sol. ∴ (C)
Prob 15. Which will give a yellow precipitate with iodine & alkali?
(A) 2 – hydroxyl propane (B) benzophenone
(C) o – methyl toluene (D) acetamide
Sol. ∴ (A)
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