一氯代物有2种，二氯代物有4种的烃是( )
A．丙烷
B．2甲基丙烷
C．丙烯
D．苯
答案：A
题目分析：A．丙烷分子中有2种H原子，其一氯代物有2种，为CH3CH2CH2Cl，CH3CH(Cl)CH3，CH3CH2CH2Cl中含有3种H原子，再次一氯取代有3种产物，CH3CH(Cl)CH3中含有2种H原子，再次一氯取代有2种产物，其中有两种为同一物质，故丙烷的二氯代物有4种，故A符合。B选项，2-甲基丙烷分子中都有2种H原子，其一氯代物有2种，为(CH3)2CHCH2Cl，(CH3)3CCl，(CH3)2CHCH2Cl中含有3种H原子，再次一氯取代有3种产物，(CH3)3CCl中含有1种H原子，再次一氯取代有1种产物，其中有两种为同一物质，故2-甲基丙烷的二氯代物有3种，故B不符合；D选项，苯分子中只有1种H原子，其一氯代物只有1种，故D不符合
Many teenagers have hobbies. But sometimes these hobbies can get in the way of schoolwork, and parents might worry about their child’s success at school. Teenagers often think they should be allowed to practice their hobbies as much as they want. Do you agree? Liu Yu, a fifteen-year-old boy from Shandong, is a running star. He is on his school running team and has always wanted to be a professional athlete. 小题1:________________ “Of course we want to see Liu Yu achieve his dreams,” says Mr Liu, “and we know how much he loves running. That’s great, and my wife and I have watched him in every one of his races. 小题2:. ________________ But we do think that our son needs to be realistic. Now that he is getting older, he needs to think about what will happen小题3:. ________________.” Liu Yu doesn’t really agree. “Well, I think I should be allowed to make decisions for myself,” he says. “My parents have always taught me the importance of working hard and not just to do what I enjoy. I understand this. 小题4:. ________________ Being a professional runners is the only thing I have ever wanted to do.” Mr and Mrs Liu believe that Liu Yu should study hard in the evenings, and so they don’t allow him to practice running on school nights. “I know this seems strict,” says Mrs Liu, “but we think we’re doing the right thing. He has to understand that very few people can become professional athletes. It’s very difficult dream to achieve. We don’t allow him to practice every day 小题5:________________”
|
|