第6题: [单项选择]下列化合物中能使Kedde试剂产生阳性反应的为( ) A. 黄酮苷 B. 洋地黄毒苷 C. 甘草皂苷 D. 香豆素苷 E. 生物碱 参考答案:B 答案解析:[解析] 作用于α、β不饱和内酯环的反应,甲型强心苷在碱性醇溶液中,双键由20(22)转移到20(21),生成C22活性亚甲基,能与下列活性亚甲基试剂作用而显色,乙型强心苷不能产生活性亚甲基,故无此类
第26题: [单项选择]Questions 19 to 22 are based on the conversation you have just heard. A. To inform him of a problem they face. B. To request him to purchase control desks. C. To discuss the content of a project report. D. To ask him to fix the dictating machine 参考答案:A