问题
单项选择题
利用生物碱或成盐溶解度不同或特殊官能团分离生物碱，四氯化碳可用于分离( )
A．苦参碱和氧化苦参碱
B．汉防己甲素和乙素
C．莨菪碱和东莨菪碱
D．小檗碱及其共存生物碱
E．麻黄碱和伪麻黄碱
答案
参考答案：C
解析： 莨菪碱亲脂性较强，可溶于四氯化碳，东莨菪碱亲脂性较弱，难溶于四氯化碳。
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利用生物碱或成盐溶解度不同或特殊官能团分离生物碱，四氯化碳可用于分离( )
A．苦参碱和氧化苦参碱
B．汉防己甲素和乙素
C．莨菪碱和东莨菪碱
D．小檗碱及其共存生物碱
E．麻黄碱和伪麻黄碱
参考答案：C
解析： 莨菪碱亲脂性较强，可溶于四氯化碳，东莨菪碱亲脂性较弱，难溶于四氯化碳。
Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.
One-quarter of today’s student population are suffering from symptoms of depression. Of that group, almost half will experience depression intense enough to call for __43___ help. But many reject that idea, because they don’t want people to think there is something wrong with them. There are three reasons why today’s college students are suffering more than in earlier ____44___. First is a weaker f  amily support structure. Today, with high divorce rates and many parents __45___ their own psychological difficulties, the traditional family is not always available for help. Another problem is __46_____ pressure. In the past ten years education costs have risen about 66 percent at public colleges and 90 percent at private schools. __47_____, most students must work part-time. A final cause of students’ depression is the large __48_____ of majors available. Because of the difficulty of ___49___ a major, college can prove a time of great indecision. Many students ___50____ majors. As a result, it is becoming common for them to take five or six years to get a degree. It can be disappointing to students to be faced with the __51____ costs. |