So let's have a clicker question here on how many total pi bonds do you expect to see in benzene?

让我们来做个课堂习题,你们觉得苯环里有一共多少个π键？

麻省理工公开课 - 化学原理课程节选

But, of course, what you saw in recitation, and hopefully, what you can now think very quickly by looking at this, is that this is not the only configuration of pi bonds that we could have in benzene.

当然，你们在习题课看到过，你们通过看这个可以很快的想到，这不是苯环里,唯一的π键构型。

麻省理工公开课 - 化学原理课程节选

How many pi bonds would you expe PROFESSOR: Two, great.

你们预计它有几个π键,两个，很好。

麻省理工公开课 - 化学原理课程节选

This is in direct contrast to when we're thinking about pi bonds.

这和π轨道,是截然相反的。

麻省理工公开课 - 化学原理课程节选

Remember, we didn't hybridize the 2 p y orbital, so that's what we have left over to form these pi bonds.

记住，我们并没有杂化2py轨道，这是我们剩下的那个行成了π键。

麻省理工公开课 - 化学原理课程节选

So, we're going to see two pi bonds.

我们可以看到两个π键。

麻省理工公开课 - 化学原理课程节选

So pi bonds have electron density both above and below the bond axis, but they actually have a nodal plane at this z, this bond axis here.

键在键轴之上,和之下都有电子密度，但它们在z方向有节面，这是键轴的地方。

麻省理工公开课 - 化学原理课程节选

So let's think about how we can classify single and double and triple bonds, which is what we're really used to dealing with in terms of these sigma bonds and these pi bonds.

让我们想想怎么来分类单键双键,和三键，这在我们在考虑sigma键,和π键是很有用的。

麻省理工公开课 - 化学原理课程节选

We want to discuss sigma bonds and pi bonds.

我们要讨论sigma键和π键。

麻省理工公开课 - 化学原理课程节选

So, what we end up having is three of these pi -- 2 p y 2 p y bonds, we can have one between these two carbons here.

我们剩下的有三个π键-,2py2py键，在这两个碳原子之间会有一个。

麻省理工公开课 - 化学原理课程节选

There's not two bonds, that's one pi bond, and the reason is because it's 2 p orbitals coming together, and remember p orbitals have electron density above and below the axis, so when they come together, it kind of looks like one bonds, but essentially what we have here is one pi bond.

这不是两个键，这是一个π键，因为这是两个2p轨道组合而成的，记住p轨道在键轴之上,和键轴之下都有电子密度，当它们靠近时，这看着很像两个键，但本质上它是一个π键。

麻省理工公开课 - 化学原理课程节选