27. Which of the following alkyl halides reacts most rapidly via an SN1 solvolysis reaction in hot methanol?
(A)1-iodohexane
(B)1-fluorohexane
(C) (R)-2-bromohexane
(D)1-iodo-1-methylcyclohexane

23. Which of the following structures are achiral and meso?(A)1 (B)2 (C) 3(D)4

24. Which of the following best describes the carbon-chlorine bond of an alkyl chloride? (A)nonpolar； no dipole (B)polar；δ+ at carbon and δ- at chlorine (C) polar；δ- at carbon and δ+ at chlorine(D)ionic

25. Which of the following factors is favorable for nucleophilicity but not basicity? (A)highly polarizable (B)low electronegativity (C) negatively charged(D)sterically hindered

26. Which of the following compounds will undergo an SN2 reaction most readily? (A)(CH3)3CCH2I (B)(CH3)3CCl (C) (CH3)2CHI(D)(CH3)2CHCH2CH2CH2I

28. When a SN1 reaction of R-2-iodobutane takes place in hot methanol, the product ________. (A)is chiral (B)will rotate plane polarized light (C) is racemic(D)will undergo a hydride shift

29. Identify the correct name for the following structure.(A)3-methoxy-5-methylcyclohepta-1,5-diene (B)6-methoxy-1-methylcyclohepta-1,4-diene (C) 7-methoxy-5-methylcyclohepta-1,4-diene(D)4-methoxy-2-methylcyclohepta-1,5-diene

30. For which of the following alkenes will cis- and trans- isomers not exist?(A)a) only (B)b) only (C) both a) and c)(D)d) only

31. Using Zaitsev's rule, choose the most stable alkene among the following. (A)1-methylcyclohexene (B)3-methylcyclohexene (C) 4-methylcyclohexene (D) They are all of equal stability according to Zaitsev's rule.

32. Consider the constitutional isomers 2-methylbut-1-ene, 2-methylbut-2-ene, and 3-methylbut-1-ene. When each of these alkenes is subjected to catalytic hydrogenation (H2, Pt), a single product results. Which of the following best describes the structural relationship among these products? (A)The products are cis-trans isomers. (B)The products are identical. (C) The products are constitutional isomers.(D)The products are enantiomers.

33. Which of the following alkenes has the smallest molar heat of hydrogenation (ie, releases the least heat upon hydrogenation)? (A)2,3-dimethyl-2-butene (B)2-methyl-2-butene (C) trans-2-butene(D)cis-2-butene