InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Compound `(A)(C_(5)H_(10))` does not dissolve in cold conc. `H_(2)SO_(4)`. What is `(A)`?A. B. C. D. |
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Answer» Correct Answer - b Alkenes and ethyne `(CH - = CH)` dissolve in cold conc. `H_(2)SO_(4)`. So the answer is `(b)`. |
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| 2. |
Compound `(B)` is `:`A. B. C. D. All |
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Answer» Correct Answer - c Birch reductio converts `(C - = C)` to `(C = C)` in anti `-` addition of `H_(2)`. So, the stereochemistry around both the double bonds should be trans and the anser is `(c)`. |
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| 3. |
The decreasing order of reactivity towards electrophilic addition (e.g. addition of `HX,X_(2),` etc.) of the following is `:` `I. CH-= CH` `II. CH_(2)=CH_(2)` `III.` `H_(2)C=CH-Cl` `IV` A. `(II)gt(I)gt(III)gt(IV)`B. `(I)gt(II)gt(III)gt(IV)`C. `(IV)gt(III)gt(I)gt(II)`D. `(IV)gt(III)gt(II)gt(I)` |
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Answer» Correct Answer - a The order of electrophilic addition `(EA)` is `:` alkene `gt` alkyne. But if alkene has `EWG`, reactivity of alkene is less than that of alkyne. Due to `EWG`, `vec(e)` dencity at `(C=C)` or nucleophilicity decreases, so addition of electrophile to `(C=C)` is slow. So the decreasing order of `EA` is `:` `(II)(`alkene `)gt(I)(`alkyne `)gt(III)(`alkene with one `EWG)gt(IV)(`alkene with two `EWG)` |
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| 4. |
Give the decreasing order or reactivity for the elimination with strong bases of `RX(X=F,XI,Br, `and `I). ` `b.` How is this information important to decide between `E2` and `E1cB`? |
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Answer» Whenever `R.D.` transition step involves breaking of the `(C-X)` bond, the rate is directly related to the leavvbility of `X^(Θ)`, which in turn is related to its basicity. The weakest base is the bast leaving group and is in the following order`:` `I^(Θ) Br^(Θ)gtCI^(Θ)gtF^(Θ)` The order of reactivity is `RIgtRBrgtRCIgtRF`. `b.` In `EIcB`, the expulsion of `C^(Θ)` occurs in the fast second step and the rate of the overall reaction is independent of the leavability of `X`. Therefore, all `RX` react with the same rate. In `E2` the expulsion of `X^(Θ)` occurs in the `R.D.S.` and the nature of `X` influences the rate. |
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| 5. |
`H_(2)O_(2)+overset(Θ)(O)H`A. B. C. D. |
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Answer» Correct Answer - A When both the `C` atoms are `2^(@)` as in compound `(A)`, diborane preferentially attacks on the `C` atom with smaller `(R )` group and exclusive product arises from bonding at the `C` atom with smaller `(R)`group because bulky diborane is more sensitive to steric effects. |
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| 6. |
Which of the following statements is `//` are correct ?A. B. C. The rate of catalytic hydrogenation of `(I)` is faster than that of `(III)`.D. In `(I)`, the exo`-` approach of two `D` atoms is from the less`-` hindered side, whereas in `(III)` , the syn `[(CH_(3)`, group `)]` hinders the exo`-` approach, so the two `D` atoms are in endo`-` position. |
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Answer» Correct Answer - a,c,d The statement `(D)` is the explanation of all parts. |
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| 7. |
The product is `:`A. B. C. D. All |
| Answer» Correct Answer - a | |
| 8. |
Assertion: Addition of `Br_(2)` to `1`-butane gives two optical isomers. Reason: The product contains one asymmetric carbon atoms.A. Statement `I` is true, Statement `II` is true, Statement `II` is the correct explanation of Statement `I`.B. Statement`I` is true, Statement`II` is true, Statement `II` is not the correct explanation of Statement `I`.C. Statement `I` is true, Statement `II` is false.D. Statement `I` is false, Statement `II` is true. |
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Answer» Correct Answer - A `CH_(3)CH_(2)CH=CH_(2)+Br_(2)rarrCH_(3)CH_(2)-overset(Br)overset(|)underset(**)(C)H-underset(Br)underset(|)(C)H_(2)` Number of optical isomers `=2^(n)=2^(1)=2.` Hence, both statement `(I)`and statement `(II)` are correct and statement `(II)` is the correct explanation of statement `(I)`. |
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| 9. |
Which reagent cannot be used for the above conversion ?A. B. `Et_(3)N`C. `POCl`D. `NH_(3)` |
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Answer» Correct Answer - c `POCl_(3)` is used for the dehydration of alcohol to alkene, others `(a), (b), `and `(c)` are used for the dehydrohalogenation of alkyl halide to alkene. |
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| 10. |
Which of the following compound are called unsaturated compounds `-` that is , it /they add /s `H_(2)` catalytically at ordinary condition of temperature ?A. B. C. D. |
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Answer» Correct Answer - a,b Highly strained cyclopropane can undergo catalytic hydrogenation under ordinary condition of temperature to give propane, but cyclobutane, cyclopentane, and cyclohexane cannot undergo the same. So, cyclopropane is called unsaturated compound. |
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| 11. |
Which of the following statements is `//` are correct ?A. `(I)` and `(IV)` are meso`-` compounds.B. `(II)` and `(III)` are enantiomers.C. `(I)` is very slow `(` or does not react `)` with alc. `KOH` in an `E2` reaction to give alkene.D. `(IV)` is very slow `(` or does not react `)` with alc. `KOH` in an `E2` raction to give alkene. |
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Answer» Correct Answer - a,b,c Iosmer `(I)` is slow to react in an `E2` reaction because in its more stable conformation, all the broming atoms are in equatorial position and an anti`-` periplanar transition state cannot be achieved, `i.e.` in isomer `(I)` there is not even a single `H` and `Cl` in anti`-` positoin for elimination reaction to occur. |
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| 12. |
Refer to Question. If `(A)` and`(C)` both show optical and geometrical isomers, which of the following statements is `//` are correct ?A. `(A)` and `(C)` are the same compound which is B. `(A)` and `(C)` are the same compound which is C. D. |
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Answer» Correct Answer - a,c The statement `(a)` and `(c)` are explanation in themselves. |
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| 13. |
Which of the following compounds would have the same vapour pressure ? A. `(I)`and `(II)`B. `(II)` and `(III)`C. `(III)` and `(IV)`D. `(II)` and `(IV)` |
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Answer» Correct Answer - c., `(III)` and `(IV)` are enantiomers and have the same physical and chemical properties, so they have the same vapour pressure. |
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| 14. |
Compound `(A)(C_(13)H_(24)O)` is a sex `-` attractant pheromone two molar equivalents of `H_(2)` and is converted to `3-`ethyl`-7-`methyl decan `-1-`ol. On reductive ozonolysis, it gives the following compounds. The numberos stereoisomers for `(A)` is `:`A. 2B. 4C. 6D. 8 |
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Answer» Correct Answer - d Two structural isomers each containing two double bonds, with different terminal groups. `{:(four G.I. for A_(1) ),(four G.I. for A_(2)):}]` |
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| 15. |
Moist ethylene can be dried by passing it through concentrated suphuric acid. |
| Answer» False. Ethylene on reaction with sulphuric acid gives ethyl hydrogen sulphate. Thus, moist ethylene can be dried by `P_(2)O_(5)` | |
| 16. |
Stabilities of alkanes can be compared by converting these compounds to a common product and comparing the amount of the heat given off. One possiblitiy would be to measure the heat of combustion from converting alkenes to `xo_(2)` and `H_(2)O` . The heats of combustion are of large values and measuring small difference in these large numbers is difficult. Alkene of the lowest heat of combustion among isomeric alkenes is of the lowest energy and is most stable. Th stability of alkenes is often compared by meansuring the ehat of hydrogenation `9` heat given off, `Delta H_(h)^(@)` during catalytic hydrogenation. The heat of hydrogenation is in smal number, which provides more accurate energy difference. For a compound containing more than one double bond, `Delta_(h)^(@)` is the sum of heat of hydrogenation of individual double bonds. For non `-` conjugated diens, this additive relatioship is found to hold. For conjugated dienes, however, the measured value is slightly lower than expected. Cumulated dienes, which are even less stable than non `-` conjugated dienes. The more stable is the alkene, lower is the heat of combustion and heat of hydrogenation. More highly substituted double bonds are usually more stable. In case of cyclokanes, compounds having higher angle strin are less stable. Which statement is false `?`A. Hydrogenation is an exothermic reaction.B. Heat of hydrogenation is better than heat of combustion for meansuring the stabilities of alkenes.C. Among the isomers alkene, the most stable alkene has the lowes heat of hydrogenation and the highest heat of combustion.D. Among the isomeric alkenes, the most stable alkenne has the lowest value of heat of hydrogenation and heat of combustion |
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Answer» Correct Answer - C Statement is itself an explanation. |
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| 17. |
Stabilities of alkanes can be compared by converting these compounds to a common product and comparing the amount of the heat given off. One possiblitiy would be to measure the heat of combustion from converting alkenes to `xo_(2)` and `H_(2)O` . The heats of combustion are of large values and measuring small difference in these large numbers is difficult. Alkene of the lowest heat of combustion among isomeric alkenes is of the lowest energy and is most stable. Th stability of alkenes is often compared by meansuring the ehat of hydrogenation `9` heat given off, `Delta H_(h)^(@)` during catalytic hydrogenation. The heat of hydrogenation is in smal number, which provides more accurate energy difference. For a compound containing more than one double bond, `Delta_(h)^(@)` is the sum of heat of hydrogenation of individual double bonds. For non `-` conjugated diens, this additive relatioship is found to hold. For conjugated dienes, however, the measured value is slightly lower than expected. Cumulated dienes, which are even less stable than non `-` conjugated dienes. The more stable is the alkene, lower is the heat of combustion and heat of hydrogenation. More highly substituted double bonds are usually more stable. In case of cyclokanes, compounds having higher angle strin are less stable. In which of the following is `Delta H^_(h)^(@)` the maximum ?A. `H_(2)C=CH_(2)`B. `H_(2)C=C=CH_(2)`C. D. |
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Answer» Correct Answer - b Cumulative diene is less stable and, hence, more `DeltaH_(h)^(@)` and more `DeltaH_(C)^(@)` |
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| 18. |
Which of the following statements is/are wrong ?A. Product `(B)` is and `BrCl` reacts with pyridine to form a complex `(n-`Bromopyridinium complex `)`.B. Product `(B)` is and the complex is `(n-`Chloropyridinium complex `)`.C. Product `(C)` is and first, the electrophile `Cl^(c-)` adds to the double bond.D. Product `(C)` is and first, the electrophilic addition of `Cl^(o+)` takes place and then the nucleophile `Br^(Θ)` adds to the double bond. |
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Answer» Correct Answer - b,d The statements are self`-` explanatory. |
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| 19. |
Which of the following statements is `//` are wrong ?A. Butyl chloride `(I)` undergoes elimination reaction faster than `4-` chloro`-` but`-1-`ene `(II)`B. `(I)` gives but`-1-`ene `(III)` on elimination with alc. `NaOH` while `(II)` gives buta `-1,3-`diene `(IV)`.C. The product `(IV)(` a congregated diene `)` is more stable than the product `(III)`, a monosubstituted alkene.D. The transition states `(T.S.)` leading the products determing the relative stabilities of the product. Since the `T.S.` leading to buta `-1,3-`diene has lower `Delta G_("activation")` (free energy of the activation), so the elimination reaction of `(I)` will occur more rapidly. |
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Answer» Correct Answer - A::D The statement `a` and `d` are wrong if `T.S.` leading to buta`-1,3-`diene has low `DeltaG_(activation)`, then reaction of `(II)` will occur more rapidly. |
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| 20. |
Which of the following statements are correct ?A. Hydrogenation is an exothermic reaction.B. Heat of hydrogenation is better than heat of combustion for meansuring the stabilities of alkenes.C. Among the isomeric alkenes, the most stable alkene has the lowest heat `(` more negative value `)` of hydrogenation and the highest heat of combustion and heat of formation `(` less negative value `)`.D. Among the isomeric alkenes, the most stable alkene has the lowest value of heat of hydrogenation, heat of combustion, and heat of formation `(` more negative value `).` |
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Answer» Correct Answer - a,b,d All the statements are self`-` explanantory. |
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| 21. |
`(A)` and `(C)` are different compounds and rotate the planepolarised light in the same direction, and both are dextrorotatory. Both `(A)` and `(C)` do not show diastereomers. Which of the following statements are correct ?A. B. C. D. |
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Answer» Correct Answer - A::B::C `D.U.` of `(A)` and `(C)=1^(@),` so the answers `(a)` and `(b)` are correct. On hydrogenation, `(+)` compound can give either `(+)` or `( -)` compound. Since `(+)` and `(-)` cannot be determined from the structure, it depends on the nature of compound, so answer `(c)` is also correct. Moreover, on hydrogenation of `(A)` or `(c)`, chiral or asymetric centre has not bee produced, it was already in the compound `(A)` or `(C)`. So the product can either be `( + )` or `( - )` . |
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| 22. |
Arranbe the following compounds in the decreasing order of acidic character. `I.` Butane ,`II.` but`-1-`ene `III.` But`-1-` yne `IV.` Butan `-1-`olA. `(I)gt(II)gt(III)gt(IV)`B. `(IV)gt(II)gt(III)gt(I)`C. `(IV)gt(III)gt(II)gt(I)`D. `(I)gt(III)gt(II)gt(IV)` |
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Answer» Correct Answer - c., The order of acidic character`:` Alcohols `gt` Alkynes `gt` Alkenes `gt` Alkanes. |
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| 23. |
Explain the formation of `(A)` and `(B)` in the following reaction. `Oct-1-en eoverset(NBS+C C I_(4))underset(hv)rarrunderset((80%))((A))+underset((20%))((B))` |
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Answer» `C_(5)H_(11)-CH=CH_(2)overset (NBS//C C I)rarr` `underset(3-Bromo-1-oct a n e(20%))(C_(5)H_(11)-CH(Br)-CH)=underset(1-Bromo-2-octen e(80%))(CH_(2)+C_(5)+C_(5)H_(11)CH=CH-CH_(2)Br)` `[C_(5)H_(11)dot(C)H-CH=CH_(2)leftrightarrowC_(5)H_(11)CH=CH-dot(C)H_(2)]` The major brominated product results from the introduction of `Br` on methylene `C`, so as to get more `-` substituted brominated alkene. The shift of the double bond is an example of allylic rearrangement. |
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| 24. |
When gas `A` is passed through dry `KOH` at low temperature, a deep red coloured compound, `B` and a gas care obtained. The gas `A`, on reaction with but-2-ene, followed by treatment with `Zn//H_2 O` yields acetaldehyde. Identify `A, B` and `C`. |
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Answer» Gas `(A)` is ozone `(O_(3))`, since `(A)` on reductive ozonolysis gives acetaldehyde `(CH_(3)CHO)` Gas`(A)+KOH("Dry")overset(Low)underset(temp.)rarr underset("coloured")underset(Deep-red)((B))+underset((gas))((C))` `4O_(3)+4KOHrarr underset("Potassium")underset("ozonide")underset((B))(4KO_(3))+underset((C))(O_(2))` |
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| 25. |
Three compounds `(A), (B)` and `(C)` are given. Which statements are correct about `(A),(B),` and `(C)` ?A. The rate of catalytic hydrogenation is faster in `(A)` than in `(B)` and `(C)`.B. The rate of catalytic hydrogenation is faster in `(B)` than in `(C)`C. `(A)` has a catalytic ring whose strain on going to less `-` strained cyclopropane ring is reduced on hydrogenation. Similarly, cyclobutene ring in `(B)` on hydrogenation is reduced to less `-` streined cyclobutane ring. But, cyclopropene ring is more strained than cyclobutene ring, so faster hydrogenation is in `(A)` than in `(B)`.D. There is a little change in the rign strain when the cyclohexen ring is reduced. |
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Answer» Correct Answer - a,b,c,d The statements `(c)` and `(d)` are explanations of `(a)` and `(b)` |
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| 26. |
Explain that `(A)` readily forms an alkene with `I^(c-)` but `(B)` does not. |
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Answer» In both `(A)` and `(B)`, two `Br` are in trans position. But in `(A)`, two `Br` are in trans`-` diaxial position and capable of `E2` elimination`:` while in `(B)`, both `Br` with are in trans `-` diequatorial position and are incapable of being eliminated. (Remember that equatorial form is more stable than axial and, hence, equatorial form is less reactive than axial form.) |
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| 27. |
Stabilities of alkanes can be compared by converting these compounds to a common product and comparing the amount of the heat given off. One possiblitiy would be to measure the heat of combustion from converting alkenes to `xo_(2)` and `H_(2)O` . The heats of combustion are of large values and measuring small difference in these large numbers is difficult. Alkene of the lowest heat of combustion among isomeric alkenes is of the lowest energy and is most stable. Th stability of alkenes is often compared by meansuring the ehat of hydrogenation `9` heat given off, `Delta H_(h)^(@)` during catalytic hydrogenation. The heat of hydrogenation is in smal number, which provides more accurate energy difference. For a compound containing more than one double bond, `Delta_(h)^(@)` is the sum of heat of hydrogenation of individual double bonds. For non `-` conjugated diens, this additive relatioship is found to hold. For conjugated dienes, however, the measured value is slightly lower than expected. Cumulated dienes, which are even less stable than non `-` conjugated dienes. The more stable is the alkene, lower is the heat of combustion and heat of hydrogenation. More highly substituted double bonds are usually more stable. In case of cyclokanes, compounds having higher angle strin are less stable. Arrange the following compounds according to their increasing heat of combustion. `I.` `1-`Butene `II.` ci `-2-`Butene `III.` trans `-2-`Butene `IV.` `2-` Methyl propeneA. `(IV)gt(I)lt(II)lt(III)`B. `(I)lt(II)lt(IV)lt(III)`C. `(IV)gt(III)lt(II)lt(I)`D. `(I)lt(II)lt(III)lt(IV)` |
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Answer» Correct Answer - c The order of stability of alkene is `2-`methyl propene `gt` trans `-2-`butene `gtcis lt1-`butene. So, `DeltaH_(C)^(@)` is reverse `(` less stable and , hence, more `DeltaH_(h)^(@)` and `DeltaH_(C)^(@))` and the oder of stability is `(IV)lt(III)lt(II)lt(I).` |
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