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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. |
Give the order of `(a)` nucleophilicity `(b)` basic character, and `(c)` fugacity of the following : (i) `F^(Ө)` (ii) `Cl^(Ө)` (iii) `Br^(Ө)` (iv) `I^(Ө)`. |
| Answer» (a) and (c) : `(iv) gt (iii) gt (ii) gt (i) (I^(Ө) gt Br^(Ө) gt Cl^(Ө) gt F^(Ө))` , `(b)` reverse. | |
| 2. |
The decreasing order of the basic character of the following is : (I) `F^(Ө)` (II) `NO_3^(Ө)` (III) `H_2 O` (IV) `CH_3 OH`.A. `(II) gt (I) gt (IV) gt (III)`B. `(III) gt (IV) gt (I) gt (II)`C. `(I) gt (II) gt (III) gt (IV)`D. `(IV) gt (III) gt (II) gt (I)` |
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Answer» Correct Answer - C Acidity : `CH_3 .^+OH_2 gt H_3O^+ gt HNO_3 gt HF` `pK_a : - 2.5 -1.74 -1.4 3.2` (See to Table 4.3) Basicity : `CH_3OH lt OH_2 O lt NO_3^(Ө) lt F^(Ө)` `[(I) gt (II) gt (III) gt (IV)]`. |
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| 3. |
Which of the following statements are correct ?A. `EtO^(Ө)` is a stronger nucleophile than `overset (Ө) O H`.B. `MeO^(Ө)` is a stronger nucleophile than `overset (Ө) O H`C. `RCOO^(Ө)` is a stronger nucleophile than `ROH`.D. `MeO^(Ө)` is a weaker nucleophile than `overset (Ө) O H`. |
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Answer» Correct Answer - A::C::D Acidic character if the following is : `MeOH gt H_2 O gt EtOH` `pK_a 15.5 15.7 16` Basic and nucleophilc character is : `MeO^(Ө) lt overset (Ө) OH lt EtO^(Ө)`. |
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| 4. |
Consider the following reactions : Anti-addition takes place in :A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
| Answer» Correct Answer - B | |
| 5. |
From the following elimination reactions, predict which one is Hofmann or Saytzeff (Zaitev) type. |
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Answer» `(a),(c),( e) rArr` Saytzeff (Zaitev) type. `(b),(d) rArr` Hofmann type. |
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| 6. |
In elimination reaction, the major product is either Saytzeff (more-substituted alkene) or Hofmann product (less-substituted alkene) depending on the nature of the substrate and the nature of the base. Which statement is correct about the following reactions ? A. The major product is `(I)` by `E1` machanism.B. The major product is `(I)` by `E2` machanism.C. The major product is `(II)` by `E1` machanism.D. The major product is `(II)` by `E2` mechanism. |
| Answer» Correct Answer - A | |
| 7. |
In elimination reaction, the major product is either Saytzeff (more-substituted alkene) or Hofmann product (less-substituted alkene) depending on the nature of the substrate and the nature of the base. Refer to Q.No.14 and find out which statement is correct ?A. Both reactions proceeds by `E2` mechanism.B. Both reactions proceed by `E1` mechanism.C. Formations of (B) and (c) proceed by `E1` and `E2` mechanisms, respectively.D. Formations of (B) and (c) proceeds by `E2` and `E1` mechanism, respectively. |
| Answer» Correct Answer - A | |
| 8. |
In elimination reaction, the major product is either Saytzeff (more-substituted alkene) or Hofmann product (less-substituted alkene) depending on the nature of the substrate and the nature of the base. Which statement is wrong about the given reaction. .A. The reaction proceeds by `E1cB` mechanism.B. `EWG(-SO_3H)` stabilities the carbanion formed in the first step.C. The reaction in stereospecific but non-regioselectiveD. `PhO^(Ө)` is a stronger base than `overset (Ө) O H` ion. |
| Answer» Correct Answer - D | |
| 9. |
Consider the following reactions : Syn-addition takes place in :A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
| Answer» Correct Answer - A | |
| 10. |
In elimination reaction, the major product is either Saytzeff (more-substituted alkene) or Hofmann product (less-substituted alkene) depending on the nature of the substrate and the nature of the base. Which statement is wrong about the given reaction ? .A. The reaction is called Cope reaction and proceeds by `E1` mechanism.B. The reaction proceedsby syn-elimination.C. The reaction is stereospecific and stereselective.D. The reaction is non-stereospecific and regioselective. |
| Answer» Correct Answer - D | |
| 11. |
The formation of cyanohydrin from ketone is an example of :A. Electrophilic addtionB. Nucleophilic addtionC. Nucleophilic substitutionD. Electrophilic substitution |
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Answer» Correct Answer - B Aldehydes and ketones undergo `NA` reactions. |
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| 12. |
The rate of `SN^2` reaction depends on the effectiveness of the nucleophile in ejecting the leaving group. Nucleophilicity is the affinity for `C` atom, while basicity is the affinity for proton. In both cases, a new bond is formed. If a new bond is formed between the anion and proton, the specied acts as a base. If a new bond is formed between the anion and `C` atom, the species acts as nucleophile. Which of the following statements is wrong ? Nucleophile order of the following in weakly polar aprotic solvents, e.g., acetone is :A. `LiI gt LiBr gt LiCl gt gt LiF`.B. `CsF gt RbF gt KF gt NaF gt LiF`C. `R_4 N^(oplus) I^(Ө) gt R_4 N^(oplus) Br^(Ө) gt R_4 N^(oplus) Cl^(Ө)` (R = Butyl group)D. All |
| Answer» Correct Answer - C | |
| 13. |
`RS^(Ө)` is a stronger nucleophile and a better leaving group than `RO^(Ө)`. `RS^(Ө)` is a weaker base than `RS^(Ө)`.A. If both `(A)` and `(R )` are true, but `( R)` is the correct explanation of `(A)`B. If both `(A)` and `( R)` are true, but `(R )` is not the correct explanation of `(A)`.C. If `(A)` is true but `( R)` is false.D. If `(A)` is false but `( R)` is true. |
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Answer» Correct Answer - A Acidity : `RSH gt ROH` Basicity : `RS^(Ө) lt RO^(Ө)` When nucleophilic centres are different and belong to the same group, nucleophilicity is antiparallel to basicity. Nucleophilicity : `RS^(Ө) gt RO^(Ө)` Weaker the base, better is the leaving group. So the leaving group ability of `RS^(Ө) gt RO^(Ө)`. |
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| 14. |
The rate of `SN^2` reaction depends on the effectiveness of the nucleophile in ejecting the leaving group. Nucleophilicity is the affinity for `C` atom, while basicity is the affinity for proton. In both cases, a new bond is formed. If a new bond is formed between the anion and proton, the specied acts as a base. If a new bond is formed between the anion and `C` atom, the species acts as nucleophile. Which of the following statements is wrong ?A. The nucleophilicity order in non-polar solvents (e.g., `C Cl_4, CS_2`) of the followind is : `I^(Ө) gt Br^(Ө) gt Cl^(Ө) gt F^(Ө)`.B. The nucleophilicity order in polar protic solvents (e.g., `H_2 O`) of the following is : `I^(Ө) gt Br^(Ө) gt Cl^(Ө) gt F^(Ө)`.C. The nucleophilicity order in weakly polar protic solvents (e.g., nitro benzene, acetone) of the following is : `F^(Ө) gt Cl^(Ө) gt Br^(Ө) gt I^(Ө)`.D. The nucleophilicity order in polar aprotic solvents (e.g., `DMSO, DMF`) of the following is : `F^(Ө) gt Cl^(Ө) gt Br^(Ө) gt I^(Ө)`. |
| Answer» Correct Answer - C | |
| 15. |
In `SN^2`, solvolysis `RX` in which the solvent is a nucleophile, what is the order and molecularity of the reaction ?A. First order , unimolecularB. First order , bimolecularC. Second order , bimolecularD. Pseudo first-order , bimolecular |
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Answer» Correct Answer - D `SN^2` solvolysis reaction in bimolecular and the rate law is : Rate `= K[RX] ["Solvent"]` Since the concentration of the solvent is very large and exceeds the amount of `RX`, therefore, its concentration is constant. Hence the reaction will follow pseudo first-order rate law. |
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| 16. |
Lodide is a better nucleophile than bromide. |
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Answer» Correct Answer - 1 When the nucleophilic centres are different and belong to the same group of periodic table, nucleophilicity is antiparallel to basicity. Acidity : `Hl gt HBr` Basicity : `I^(Ө) lt Br^(Ө)` Nucleophilicity : `I^(Ө) gt Br^(Ө)`. |
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| 17. |
The halogen atom in `RX` can easily be replaced by nucleophiles such as :A. `NO_2^(Ө)`B. `RO^(Ө)`C. `CN^(Ө)`D. None |
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Answer» Correct Answer - A::B::C Strong nucleophiles such as `NO_2^(Ө), RO^(Ө)`, and `CN^(Ө)` can displace weak nucleophile, `X^(Ө)`. |
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| 18. |
(a) Give the products of the reaction of `KOH` with (i) `C_4H_9Br` (ii) `C_2H_5CHBrCH_3` (iii) `Me_3CBr` (b) Give the reactivity order. (c) Give the factors that determine the major product. |
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Answer» (a) (i) `C_2H_5CH = CH_2` (ii) trans `CH_3CH = CHCH_3` (iii) `Me_2 C = CH_2` (b) `3^@ gt 2^@ gt 1^@` (c) The most-substituted alkene is produced in a major amount as predicted by Saytzeff rule with trans dominating over cis. |
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| 19. |
An `SN^2` reaction of an asymmetric carbon of a compound always gives :A. An enantiomer of the substrateB. A product with opposite optical rotationC. A mixture of diastereomersD. A single stereoisomer. |
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Answer» Correct Answer - B Inversion occurs in `SN^2` reaction, so a product with opposite optical rotation is obtained. |
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| 20. |
Which of the following reactions will not give Hofmann alkene ?A. B. C. D. |
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Answer» Correct Answer - C `RF` with bulkyl or non-bulky base always gives Hofmann product. However. RCl with bulky base gives Hofmann but with non-bulky base gives Saytzeff product. |
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| 21. |
Which of the following is the best method for the preparation of compound cyclopentyl cyanide from cyclopentyl chloride ?A. B. `(A)+overset(Theta)(C)Nto (B)`C. D. All |
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Answer» Correct Answer - A Since `I^(Ө)` is a better leaving group, so the reaction (a) is the best method. |
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| 22. |
Which statement is correct about the following reactions ? .A. Product is by elimination reaction.B. Product is (II) by `SN^(1)` reaction.C. Product is `(II)` by `SN^1` reactionD. Both (a) and (b). |
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Answer» Correct Answer - B Same explanation as in `Q. No. 15`. |
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| 23. |
Of the following pairs, which is the faster `SN^2` reactions ? |
| Answer» Each of back-side attack (less steric hindrance) makes `SN^2` faster. In all cases, `(i)` is faster. | |
| 24. |
Which of the compound in each of the following pairs will react faster in `SN^2` reaction with `overset (Ө) O H` (A) `MeBr (I) and MeI (II)` (B) `Me_3 C - Cl (III) and MeCl (IV)` .A. `overset ((A)) ((I)) overset ((B)) ((III)) overset ((C))((V))`B. `overset ((A)) ((I)) overset ((B)) ((IV)) overset ((C))((V))`C. `overset ((A)) ((II)) overset ((B)) ((III)) overset ((C))((VI))`D. `overset ((A)) ((II)) overset ((B)) ((IV)) overset ((C))((VI))` |
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Answer» Correct Answer - D `(A) (II), I^(Ө)` is a better leaving group than `Br^(Ө)`. `(B)(V),I^@ RX` undergoes `SN^2` reaction than `3^@ RX` `(A) (VI)`, Vinyl halide `(V)` does not undergo `SN^1` or `SN^2` reaction , `(VI)` is `1^@ RX`, therefore undergoes `SN^2`. |
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| 25. |
The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by : (i) The polarisability of `(R - X)` bond. (ii) The stability of `X^(Ө)`. (iii) The degree of stabilisation through solvation of `X`. (iv) The strength of `(R - X)` bond. The leaving group tendency is also called fugacity. Which statement is correct ?A. Only `SN^1` reaction depends on the nature of leaving group.B. Only `SN^1` reaction depends on the nature of leaving group.C. Both `SN^1` and `SN^2` reactions depends on the nature of leaving group.D. All |
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Answer» Correct Answer - C The statement of self-explanatory. |
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| 26. |
Consider the following reactions : Which of the following are stereospecific reactions ?A. `(I),(II)`B. `(I),(II),(III)`C. `(III),(IV),(V)`D. All |
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Answer» Correct Answer - D All these reaction are hydroxylation reaction. All of them are stereospecific, but if one product is formed they are regioselective. If more than one products in almost major amount are formed they are non-regioselective. Syn-hydroxylation occurs in reaction `(I),(II)`, and `(V)` , whereas anti-hydroxylation occurs in reactions `(III), (IV)`, and `(VI)` `{:(,"Reactant",underset("mechanism")("Reagent"),"Product",),("a".,underset("same groups)")("cis(with two"),underset("same OH groups]")"syn [with two","Meso",),("b".,underset("same groups)")"cis (with two",underset("same OH groups]")("Anti (with two"),(pm)"or racemic",),("c".,underset("same groups)")("trans (with two)"),underset("same OH groups")"Syn [with two",(pm)"or racemic",),("d".,underset("same groups)")"trans (with two",underset("same OH groups]")"Anti [with two","Meso",):}` |
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| 27. |
Consider the following reactions : Which of the following are stereospecific reactions ?A. `(I),(II)`B. `(I),(II),(III)`C. `(III),(IV),(V)`D. All |
| Answer» Correct Answer - D | |
| 28. |
Addition of bromine to trans-2-butene yields meso-2,3-dibromobutane. Bromine addition is an electrophilic addition.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 - B trans-Alkene + Anti-addition of `Br_2 rarr` Meso compound Addition takes place by `Br^(oplus)` (electrophilic addition) Both the statements are correct but statement `II` is not the correct explanation of statement `I`. |
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| 29. |
`(+-)` -Tartaric acid is formed in :A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
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Answer» Correct Answer - A Rule `c` |
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| 30. |
Refer to Q.No. 9 above and find out the rate expression of the reaction.A. Rate `= K_1[2^@ RX][overset (Ө) O H]`B. Rate `= K_2[2^@ RX]`C. Rate `= K_1[2^@ RX][overset (Ө) O H] + K_2[2^@RX]`D. Rate `= K_1[2^@ RX][overset (Ө) O H] + K_2[2^@ RX]` |
| Answer» Correct Answer - C | |
| 31. |
Which product is racemic in the above reaction ?A. Product `B`B. Product `C`C. BothD. None |
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Answer» Correct Answer - C cis-Compound (with two different groups) `+ Syn`-hydroxylation (cold. `alk. KMnO_4`) or anti-hydroxylation `(mCPBA) rarr` Product is always racemic. |
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| 32. |
Consider the following reactions.A. B. C. D. |
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Answer» Correct Answer - D Syn-hydroxylation (stereospecific) : product is meso (one product) hence regioselective. (b) trans-Compound + Anti-hydroxylation (stereospecfic) , product is meso (one product) hence regioselective. (c) `CH_2N_2` products singlet carbene and the reaction is both stereospecific and regioselective. (d) `CH_2 = C=O` products triplet carbene and the reaction is both non-stereospecific and non-regioselective. |
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| 33. |
Consider the following reactions : Which of the following regioselective reactions ?A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
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Answer» Correct Answer - A (Rule a), only one product meso-butan-2,3-diol is formed, hence it is regioselective. |
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| 34. |
Consider the following reactions : Which of the following regioselective reactions ?A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
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Answer» Correct Answer - B (Rule d). Trans-Compound + Anti-mechanism (in `III, IV`, and `VI`] , only product meso-tartaric acid is formed and hence it is regioselective. |
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| 35. |
Rearrangement reactions are shown by :A. CarbanionB. Free radicalC. CarbeneD. Carbocation |
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Answer» Correct Answer - D Only carbocation shows rearrangement (but is same cases radical also rearranges). |
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| 36. |
Which of the following is the strongest nucleophile ?A. `EtO^(Ө)`B. `overset (Ө) O H`C. `overset (Ө) C N`D. `I^(Ө)` |
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Answer» Correct Answer - A Nucleophilicity is paralle to basicity Acidity : `Hl gt HCN gt H_2O gt EtOH` Basicity and nucleophilicity : `I^(Ө) lt overset (Ө) C N lt overset (Ө) O H lt Et O^(Ө)`. |
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| 37. |
Consider the following reactions : Racemic-butan-2,3-diol is formed in :A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
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Answer» Correct Answer - B Rule `b` |
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| 38. |
Consider the following reactions : Meso-butan-2,3-diol is formed in :A. `(I),(II),(V)`B. `(III),(IV),(VI)`C. `(I),(II),(IV)`D. `(III),(IV),(V)` |
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Answer» Correct Answer - A Rule `a` |
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| 39. |
Vinyl bromide undergoes :A. Addition reactionB. Substitution reactionC. Elimination reactionD. Rearrangement reaction |
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Answer» Correct Answer - A::C The statement is self-explanatory. |
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| 40. |
A partially racemised `(+) -` 2-bromo-octane `(2^@ RX)` on reaction with aq. `NaOH` in acetone gives an alcohol with `80 %` inversion and `20 %` racemisation. What is the percentage of back-side attack ?A. 0.4B. 0.1C. 0.9D. 0.8 |
| Answer» Correct Answer - C | |
| 41. |
Which of the following reactions are correct ?A. B. (A) (trans) `underset(SN^(1))overset(overset(Theta)(OH))to(B)(cis)`C. D. `(A) (trans) overset(H_(2)O)underset(SN^(1))to(C)(trans)` |
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Answer» Correct Answer - A::C In (a) `SN^2` reaction proceeds by inversion of configuration, so the product is cis. In polar solvent (e.g., `H_2 O`), `SN^1` reaction occurs, and reaction and racemisation take place if bond to the asymmetric `C` atom is broken. So the correct answer for `SN^1` reaction is `(c)`. |
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| 42. |
Walden inversion takes place in `SN^2` reaction. Half-life period of `SN^2` reaction is inversely proportional to the concentration of the substrate or nucleophile or both.A. If both `(A)` and `(R )` are true, but `( R)` is the correct explanation of `(A)`B. If both `(A)` and `( R)` are true, but `(R )` is not the correct explanation of `(A)`.C. If `(A)` is true but `( R)` is false.D. If `(A)` is false but `( R)` is true. |
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Answer» Correct Answer - B `T_(1//2)` of second order reaction `prop (a)^(-1)`, where (a) is the initial concentration of the reactant or nucleophile or both. |
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| 43. |
The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by : (i) The polarisability of `(R - X)` bond. (ii) The stability of `X^(Ө)`. (iii) The degree of stabilisation through solvation of `X`. (iv) The strength of `(R - X)` bond. The leaving group tendency is also called fugacity. Which of the following undergoes `SN` reaction easily ?A. Vinyl bromideB. BromobenzeneC. p-Nitro bromobenzeneD. |
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Answer» Correct Answer - C (a) Vinyl halide does not undergo either `SN^1` or `SN^2` reaction. (b) Aryl halide does not undergo `SN` reaction unless benzene ring is activated by `EWG` [e.g., `NO_2` group]. (d) Bridge-head halides are inert to both `SN^1` and `SN^2` reactions. |
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| 44. |
The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by : (i) The polarisability of `(R - X)` bond. (ii) The stability of `X^(Ө)`. (iii) The degree of stabilisation through solvation of `X`. (iv) The strength of `(R - X)` bond. The leaving group tendency is also called fugacity. Which one of the followingd has the highest fugacity ?A. Tosylate `(overset (Ө) O Ts)`B. MesylateC. Triflate `(F_3 C - SO_3^(Ө))`D. All are equal |
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Answer» Correct Answer - C It is the conjugate base (weak base) of the strongest acid `(F_3 C - SO_3 H)`. |
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| 45. |
The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by : (i) The polarisability of `(R - X)` bond. (ii) The stability of `X^(Ө)`. (iii) The degree of stabilisation through solvation of `X`. (iv) The strength of `(R - X)` bond. The leaving group tendency is also called fugacity. Which statement is correct ?A. Only `SN^1` reaction depends on the nature of leaving group.B. Only `SN^1` reaction depends on the nature of leaving group.C. Both `SN^1` and `SN^2` reactions depends on the nature of leaving group.D. All |
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Answer» Correct Answer - C The statement of self-explanatory. |
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| 46. |
The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by : (i) The polarisability of `(R - X)` bond. (ii) The stability of `X^(Ө)`. (iii) The degree of stabilisation through solvation of `X`. (iv) The strength of `(R - X)` bond. The leaving group tendency is also called fugacity. Which statement is wrong ?A. In polar aprotic solvents such as `DMSO, DMF`, and `DMA`, the fugacity order is `I^(Ө) gt Br^(Ө) gt Cl^(Ө) gt F^(Ө)`.B. Strong bases are good leaving groups.C. The leaving group order of the following is : `overset (Ө) OH gt RO^(Ө) gt CH -= C^(Ө) gt overset (Ө) NH_2`.D. Charges species are good leaving groups than neutral species. |
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Answer» Correct Answer - B Weak bases are good leaving groups. Acidic order : `H_2 O gt ROH gt CH -= CH gt NH_3` Basic order : `overset (Ө) O H lt R O^(Ө) lt CH -= C^(Ө) lt overset (Ө) N H_2` Weaker the base, better is the leaving group. Leaving group order : `overset (Ө) O H gt RO^(Ө) gt CH -= C^(Ө) gt overset (Ө) N H_2`. |
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| 47. |
The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by : (i) The polarisability of `(R - X)` bond. (ii) The stability of `X^(Ө)`. (iii) The degree of stabilisation through solvation of `X`. (iv) The strength of `(R - X)` bond. The leaving group tendency is also called fugacity. Which of the following is the wrong order of fugacity ?A. `SbH_3 gt AsH_3 gt PH_3 gt NH_3`B. `F^(Ө) gt overset (Ө) O H gt overset (Ө) N H_2 gt overset (Ө) C H_3`C. `NH_3 gt NH_2 - NH_2 gt MeNH-NH -Me gt Me_2 N-Nme_2`D. `C overset (Ө) N gt overset (Ө) OH gt MeO gt overset (Ө) CH_3`. |
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Answer» Correct Answer - D Acidic order : `HCN gt MeOH gt H_2 O gt CH_4` Basic order : `overset (Ө) C H lt MeC^(Ө) lt overset (Ө) H lt overset (Ө) C H_3` Weaker the base, better is the leaving group. Fugacity order : `overset (Ө) C N gt MeO^(Ө) gt overset (Ө) O H gt overset (Ө) C H_3`. |
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| 48. |
Of the following pairs, which is the faster `SN^1` reactions ? . |
| Answer» Formation of the more stable carbocation makes `SN^1` faster. In all cases, `(i)` is faster. | |
| 49. |
Which of the following would give a better yield of ether ? . |
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Answer» (a) (`SN^2` attack of nucleophile `1^@ C`). (b) (`SN^2` attack of more hindered `2^@ C`) Reaction `(a)` would give a better yield while `(b)` is also accompained by elimination. |
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| 50. |
Which of the following statements/reactions are correct ?A. `SN^2//E2` ratio is higher with `RS^(Ө)` than for those with `RO^(Ө)`.B. `SN^2//E2` ratio is highest for `1^@ RX` and least for `3^@ RX`.C. D. `Me_3 C - Br + KCN rarr Me_3 C - CN`. |
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Answer» Correct Answer - A::B::C (a) `RS^(Ө)` is a stronger nucleophile than `RO^(Ө)` but is a weaker base than `RO^(Ө)` [as explained in (b) above] So, `SN^2` is more predominant than `E2`, and consequency `SN^2//E2` ratio is higher. (b) `1^@ RX` undergoes `SN^2` reaction and `3^@` undergoes `SN^1` and `El` reactions. So `SN^2//E2` is higher for `1^@ RX` (c) `EtO^(Ө)` is a stronger base, so `E2` reaction is prediominant to give (I) as the major product. (d) With `overset (Ө) CH` (acting both as nucleophile and base) both `SN^1` and `El` reactions may occur. Hence the product formed by `SN^1` reaction in wrong. It would give elimination product also. |
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