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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

試題詳情

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

試題詳情

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

試題詳情

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

試題詳情

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

試題詳情

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

試題詳情

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

試題詳情

2.I________at my watch and was surprised to see that it was nearly midnight.

A.glanced              B.observed

C.glared              D.stared

試題詳情

1.They are ready to take________action regardless of________consequence.

A./;a       B.the;the

C./;the               D.an;the

試題詳情

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

試題詳情


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