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 用分子量為43的烷基取代甲苯苯環(huán)上的一個氫原子所得的芳香烴產物數(shù)目為( )
A、3種 B、4種 C、5種 D、6種
解析:烷基的通式為-CnH2n+1,M=43,由12n+2n+1=43。解得n=3,C3H7-烴基可能有兩種:
CH3-CH2-CH-和
它們可分別取代苯環(huán)上鄰、間、對位上的氫原子。甲苯有三個不對稱位置,
故兩種不同的烴基取代苯環(huán)上的一個氫原子,得到的同分異構體數(shù)目為2×3=6(種)。
答案:D
例6 1,2,3-三苯基環(huán)丙烷的3個苯基可以分布在環(huán)丙烷平面的上下,因此有如下2個異構體。
[是苯基,環(huán)用鍵線表示,C、H原子都未畫出 ]
據(jù)此,可判斷1,2,3,4,5-五氯環(huán)戊烷(假定五個碳原子也處于同一平面上)的異構體數(shù)是( )
A、4 B、5 C、6 D、7
解析:從1,2,3-三苯基環(huán)丙烷的結構可以看出苯環(huán)可處于平面的上方或下方。可以得出:
①氯全部在面上(或面下),1種
②4個氯在面上,1個氯在面下,1種。
③3個氯在面上,2個氯在面下,2種。
答案:A
變形題
鄰甲基苯甲酸 有多種同分異構體,其中屬于酯類,且分子結構中有
甲基和苯環(huán)的異構體有( )
A、2種 B、3種 C、4種 D、5種
解析;據(jù)題目要求,同學們要注意苯環(huán)不能拆,那么只能改變苯環(huán)上的兩個取代基。一般來講,大家很容易看出-COOH和-CH3組合成-COOCH3,而容易忽略-COOH與-OOCH的區(qū)別,前者應為羧酸,而后者為甲酸某酯,故有異構體:
答案:D
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