14. Increasing the temperat greatly the rate of the reaction. The most ure of a
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14. Increasing the temperat greatly the rate of the reaction. The most ure of a chemical reaction usually increases this is that increasing the temperature A) the collision frequency B) the probability factor c) the fraction of collisions with energy greater D) the energy of activation. B) the amount of heat released in the reac important reason tor increases: than Bact action 15. Which is the weakest nucleophile in polarap A) I D) F B) Br 16. Which of the followingis the poorest leaving group? A) H B) Ci c) H20 D) E) 0 O-S-R 17. Teeat lnag (c eich a mixture ot H20 and CH,OfH at room temperature would yield: A) CH2-C(CH3 2 D) All of these E) None of these (CH3) 3COH c) (CH3) 3COCH3 Nu-R + L-, are 18. SN1 reactions of the type, Nu- + RL- favored: A) when terti B) by using a high concentration of the nucleophile. C) when L is a strong base D) by use of a non-polar solvent. B) by none of the above substrates are used. 19. Which of the following is a substitution reaction? B) CH3CH3 + Cl2 C) CH3 CH2C1 + OH Oly-CH2 + H2O + Cl- D) More than one of the above B) None of the aboveExplanation / Answer
14. (c) More the collisions of Energy > Eact, greater is the rate of the reaction.
Reaction only result when the particles collide with Energy > Eact,
15. (a) I- will be the weakest Nucleophile in polar aprotic solvents.
In polar aprotic solvents, there will be no hydrogen bonding of anions with the solvents i.e no shielding of solvent shell around the anion. smaller the size better the nucleophile.Nucleophilicity trend in halides in polar aprotic solvents: F- > Cl- > Br- > I-
16.(a) Hydride ion H- is the poorest leaving group.
As per the conjugate acid base theory, strong acid produce weak conjugate base.
Weaker the conjugate base stronger the leaving tendency.
Or stronger the conjugate base (weak acid) poorest the leaving tendency.
The weekest conjugate acid in the options is H2 (H- conjugate base).
17. (D) All of these are possible.
(Me)3C-OH and (Me)3C-OMe via SN1 reaction and CH2=C(CH3)2 via E1 mechanism.
18. (a) SN1 reactions are favored for Tertiary substrates due to the formation of Stable 3o Carbocation.
19. (D) More than one of the above.
(A) and (B) are substitution reactions while (C) is elimination.
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