定语从句中经常有介词+which的情况,那这时WHICH指代的先行词是不是 不可以是一整个句子,只能是一个词,

Danger is drawing near of which he is not aware.这句话可能语法上说得过去,但是听起来很别扭.可以还原成两句话,He is not aware of the danger.The danger is drawing near.或一句话,像你说的,但加个“that"就更清楚.He is not aware of that danger is drawing near.
如果这句话是：Danger is drawing near,about which he is not aware.可能更好.注意：be aware of 是知道的意思,但aware 本身也是个形容词,是察觉的,知觉得,有认识的.
再举个例子:She wrote a book of which I have forgotten the name.可以还原成两句话,She wrote a book.I have forgotten the name of the book.这个句子中的“of"和你例句中的“of"不同,这个是表示所有格.这种形式是常用的.这句话中,which 就是指前面的先行词.但用逗号和前一句话分开（非限制性）,which也可以指一个句子.