So in order to rotate a double bond, you have to actually break the pi bond, so essentially what you're doing is breaking the double bond.

为了能够旋转双键，你必须打破一个π键，本质上我们要做的就是打破双键。

麻省理工公开课 - 化学原理课程节选

So for b 2, which is a single bond, that's 289 kilojoules per mole to break it, and it takes us more energy to break this double bond for carbon, which is 599 kilojoules per mole.

对于B2，它是单键，需要289千焦每摩尔来打破它，而对于碳双键,打破它要更多的能量，等于599千焦每摩尔。

麻省理工公开课 - 化学原理课程节选

That tells you something about the physical chemistry of the molecule; that it's these hydrogen bonds that hold the double strands and I can break those down under certain conditions.

我们从中可以知道一些,DNA分子的理化特点,双链是由氢键连接在一起,在一定条件下这些氢键可以断裂

耶鲁公开课 - 生物医学工程探索课程节选