"It could be hitting natural fractures that already exist." Fox notes that toxic gases like benzene,toluene and hexane also accompany natural gas extraction.

VOA: standard.2010.01.02

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

So, let's look at this in a more simple structure here where we have the two possible forms of benzene, and the reality is is that it's going to be some combination of the two.

让我们从一个更简单的结构,来看看这两种可能的苯环构型，实际情况,是这两个的组合。

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

I think most and you have talked a little bit about benzene over this past week in recitation.

我想你们大多数人,都在这周的习题课上讨论过苯环。

麻省理工公开课 - 化学原理课程节选

All right, so let's think of a more complicated example of having a double bond, and maybe a more interesting example, and this is talking about benzene.

好了，让我们来看关于双键的,一个更复杂的例子，也许是更有趣的例子，我们要讨论苯环。

麻省理工公开课 - 化学原理课程节选

So, of course, this is resonance so we can go ahead and put our resonance notation in there to indicate that benzene is a resonance structure.

当然，这是共振的,所以我们可以在这里标上共振记号,表明苯环是一个共振结构。

麻省理工公开课 - 化学原理课程节选

Benzene is a ring that's made up of six carbon atoms and six hydrogen atoms.

苯环是一个由六个碳原子,和六个氢原子组成的环。

麻省理工公开课 - 化学原理课程节选

So that's two of our types of bonds in benzene, and we have one type left, that's going to actually be the double bond or the pi bond that So we can have one bond here between this carbon's p orbital and this carbon's p orbital.

这就是苯环里的两种键，我们还剩一种，那就是这些p轨道之间，形成的双键或者π键,我们可以在这个碳的p轨道,和这个碳的p轨道之间有个键。

麻省理工公开课 - 化学原理课程节选