9.You have made a few mistakes in your composition but______,it’s well written.
A.first of all B.on the whole
C.on the other hand D.so far
8.Most of the students in our class like to read China Daily,which________every day.
A.comes out B.comes up
C.come across D.comes about
7.-How do you find the football match between England and Italy?
-There is nothing special-it is only________.
A.average B.usual
C.typical D.normal
6.Quantities of water________for cooling in the only one of the plants that________steel.
A.has been needed;produces
B.are needed;produces
C.is needed;produce
D.have been needed;produce
5.-She should not have done that sort of thing.
-Whatever she did was reasonable,________to what you have done.Besides,it’s none of your business.Get down to________your lessons.
A.compared;doing B.comparing;doing
C.compared;do D.comparing;do
4.________for her,Chen Zhong,the last champion,had no chance to take part in the finals.
A.Luckily B.Unfortunately
C.Obviously D.Absolutely
3.-Lucy looks blue today.
-Yes,but I don’t know what it is________makes her so upset.
A.as B.what
C.that D.which
2.I________at my watch and was surprised to see that it was nearly midnight.
A.glanced B.observed
C.glared D.stared
1.They are ready to take________action regardless of________consequence.
A./;a B.the;the
C./;the D.an;the
例5 用分子量为43的烷基取代甲苯苯环上的一个氢原子所得的芳香烃产物数目为( )
A、3种 B、4种 C、5种 D、6种
解析:烷基的通式为-CnH2n+1,M=43,由12n+2n+1=43。解得n=3,C3H7-烃基可能有两种:
CH3-CH2-CH-和
它们可分别取代苯环上邻、间、对位上的氢原子。甲苯有三个不对称位置,
故两种不同的烃基取代苯环上的一个氢原子,得到的同分异构体数目为2×3=6(种)。
答案:D
例6 1,2,3-三苯基环丙烷的3个苯基可以分布在环丙烷平面的上下,因此有如下2个异构体。
[是苯基,环用键线表示,C、H原子都未画出 ]
据此,可判断1,2,3,4,5-五氯环戊烷(假定五个碳原子也处于同一平面上)的异构体数是( )
A、4 B、5 C、6 D、7
解析:从1,2,3-三苯基环丙烷的结构可以看出苯环可处于平面的上方或下方。可以得出:
①氯全部在面上(或面下),1种
②4个氯在面上,1个氯在面下,1种。
③3个氯在面上,2个氯在面下,2种。
答案:A
变形题
邻甲基苯甲酸 有多种同分异构体,其中属于酯类,且分子结构中有
甲基和苯环的异构体有( )
A、2种 B、3种 C、4种 D、5种
解析;据题目要求,同学们要注意苯环不能拆,那么只能改变苯环上的两个取代基。一般来讲,大家很容易看出-COOH和-CH3组合成-COOCH3,而容易忽略-COOH与-OOCH的区别,前者应为羧酸,而后者为甲酸某酯,故有异构体:
答案:D
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