Name: Diels-Alder: endo rule | 有機化學 | 可汗學院 (Diels-Alder: endo rule | Organic chemistry | Khan Academy)
Uploaded: 2025-04-18T07:11:35.000Z
Duration: 9 min 56 s

to 不定詞

On the left is our diene, this is cyclopentadiene, and we have this bridging CH2 to think about.

左邊是我們的二烯，這是環戊二烯，我們要考慮的是橋接的 CH2。

On the right is our dienophile, and we have these two aldehydes that are cis to each other.

右邊是我們的親二烯，我們有兩個互為順式的醛。

動名詞

So in this video, we have stereochemistry for the diene and the dienophile, and we're also gonna talk about the endo and exo products.

在本視頻中，我們將介紹二烯烴和親烯烴的立體化學，還將討論內生產物和外生產物。

But first, let's just think about our Diels-Alder reaction without any stereochemistry.

但首先，讓我們考慮一下沒有任何立體化學的 Diels-Alder 反應。

So we're gonna move our six pi electrons around.

所以我們要把六個π電子移動一下。

Take these pi electrons, and we're gonna move them into here to form a bond between these two carbons.

把這些π電子移到這裡，在這兩個碳之間形成一個鍵。

These pi electrons are gonna form a bond between these two carbons, and finally, these pi electrons are going to move down.

這些 pi 電子會在這兩個碳之間形成一個鍵，最後，這些 pi 電子會向下移動。

So if we draw the product, again, not worrying about stereochemistry, we put our double bond in here, and then these aldehydes, I'm going to abbreviate as CHO.

是以，如果我們畫出產物，同樣不用擔心立體化學問題，我們把雙鍵放在這裡，然後把這些醛縮寫為 CHO。

So we have CHO, and then another aldehyde down here, so CHO.

所以我們有 CHO，然後下面還有一個醛，所以是 CHO。

We can put in our bridging CH2, so I'll just draw that in, and let's follow our pi electrons.

我們可以把橋接的 CH2 放進去，所以我會把它畫進去，然後讓我們跟著π電子走。

So our pi electrons in red formed a bond here.

是以，紅色的π電子在這裡形成了一個鍵。

Our pi electrons in blue formed this bond, and our pi electrons in magenta formed this bond.

藍色的π電子形成了這個鍵，品紅色的π電子形成了這個鍵。

But notice, for our product, we haven't really shown any stereochemistry.

但請注意，對於我們的產品，我們並沒有真正展示任何立體化學。

那麼，太空中的這些醛類物質在哪裡呢？

它們與橋接的 CH2 有什麼關係？

Well, let's say the diene and the dienophile approach each other in this way.

那麼，假設二烯和親二烯以這種方式相互靠近。

So we know that a bond forms here, so this bond in red, so that's a bond that forms between this carbon and this carbon, so that bond forms in here, and for the product, here you can see that bond.

是以，我們知道這裡形成了一個鍵，紅色的鍵是這個碳和這個碳之間形成的一個鍵，是以這個鍵在這裡形成，而對於生成物，你可以在這裡看到這個鍵。

And then we also have this bond in blue, which forms between this carbon and this carbon, so it's a bond that forms in here, and here is that bond on our product.

然後我們還有一個藍色的鍵，它在這個碳和這個碳之間形成，所以它是在這裡形成的一個鍵，這裡就是我們產品上的那個鍵。

We need to think about the stereochemistry of the diene first, so we look at our cyclopentadiene, and we have this bridging CH2.

我們首先需要考慮二烯的立體化學，所以我們看一下環戊二烯，我們有這個橋接的 CH2。

We know that inside substituents go up, so on our model set, here is that CH2, and here are the bonds that are leading to it.

我們知道里面的取代基是向上的，所以在我們的模型集上，這裡是 CH2，這裡是通向它的鍵。

And when we form our product, that CH2 goes up in space.

當我們形成產品時，CH2 就會進入太空。

Next, we need to think about the stereochem of our dienophile, so we have a double bond, we have hydrogens on the left side, and if we draw a line here, we saw how to deal with this in earlier videos.

接下來，我們需要考慮親二烯的立體化學性質，是以我們有一個雙鍵，左邊有氫，如果我們在這裡畫一條線，我們在之前的視頻中看到過如何處理這個問題。

The stuff on the left side goes down, so these hydrogens, if we follow them along, so here are the hydrogens, and we can see them in our final product, and if we're staring at the final product in this direction, those hydrogens are going away from us in space, so the hydrogens would be down.

左邊的東西會向下移動，所以這些氫，如果我們跟著它們走，這裡就是氫，我們可以在最終產品中看到它們，如果我們盯著最終產品的這個方向看，這些氫在空間中會遠離我們，所以氫會向下移動。

And these aldehydes here, so these aldehydes, I've made red in the model set, so here you can see the red, which is just standing in for our aldehyde, and those aldehydes end up on the same side, and if we're staring down this way, here are the aldehydes, those are actually coming out at us.

這些醛在這裡，所以這些醛，我在模型集中做成了紅色，所以在這裡你可以看到紅色，它只是代表我們的醛，這些醛最終在同一側，如果我們盯著這邊看，這裡是醛，這些醛實際上是衝著我們來的。

So when we draw in our product, let's go ahead and start drawing this in here, we'd have a bicyclic compound, so we'd sketch that in, and we have our bridging CH2, so let's put that in, we have our double bond here, and then we have our aldehydes.

是以，當我們繪製我們的產品時，讓我們繼續開始繪製，我們會有一個雙環化合物，是以我們會勾畫出它，我們有橋接的 CH2，是以讓我們把它放進去，我們在這裡有雙鍵，然後我們有醛。

Our aldehydes are up, so at this carbon, we need to draw in an aldehyde up, so CHO, we have a hydrogen that's down, so let's put in our hydrogen going down at this carbon, and then we have, at this carbon, an aldehyde going up, so CHO, and then a hydrogen going down.

我們的醛是向上的，所以在這個碳上，我們需要引出一個向上的醛，所以 CHO，我們有一個向下的氫，所以讓我們在這個碳上加入向下的氫，然後在這個碳上，我們有一個向上的醛，所以 CHO，然後一個向下的氫。

So this is the exo product, so this is said to be the exo product, because we have our aldehydes up, our bridging CH2 is up, and then here is our double bond, so that's one of the possible products.

這就是外向產物，所以說這是外向產物，因為我們的醛在上面，橋接的 CH2 在上面，然後這裡是我們的雙鍵，所以這是可能的產物之一。

What about if our dienophile approaches in this direction?

如果我們的嗜食者朝這個方向靠近呢？

So if we have our hydrogens here on our double bond, and we draw a line, we know the stuff on the right side of the double bond ends up, so here are the two hydrogens, and when those two bonds form right in here, these hydrogens are up, if you're staring down this way.

是以，如果我們在雙鍵上畫一條線，我們就會知道雙鍵右側的東西是向上的，所以這裡有兩個氫，當這兩個鍵在這裡形成時，這些氫就是向上的，如果你盯著這邊看的話。

The stuff on the left side of the double bond now, our aldehydes are on the left side, so here are the aldehydes, and when our product is formed, we're looking this way, the aldehydes are going away from us in space, the aldehydes are down.

雙鍵左側的東西，我們的醛在左側，所以這裡是醛，當我們的產物形成時，我們看這邊，醛在空間中遠離我們，醛是向下的。

Let's draw in this product, so we have our bicyclic, let me go ahead and draw that in here, so here is our bicyclic with our bridging CH2, our double bond is in the back, and now when we're drawing these in, the hydrogens are up, so at this carbon, there's a hydrogen up, and then there's an aldehyde going down, so here is our CHO going down, same thing at this carbon, so a hydrogen's going up, and an aldehyde is going down.

讓我們畫出這個產物，所以我們有雙環，讓我繼續畫，這裡是我們的雙環，我們的橋接 CH2，我們的雙鍵在後面，現在當我們畫出這些時，氫在上面，所以在這個碳上，有一個氫在上面，然後有一個醛在下面，所以這裡是我們的 CHO 在下面，在這個碳上也是一樣，所以一個氫在上面，一個醛在下面。

This is called the endo product, so let me write that in here, so this is endo.

這就是所謂的內臟產品，讓我把它寫在這裡，這就是內臟。

Our aldehydes are going down, our bridging CH2 is up, and here is our double bond.

我們的醛向下，橋接的 CH2 向上，這裡是我們的雙鍵。

It turns out the endo product is the preferred product most of the time, and this is called the endo rule, or the alder endo rule, and it's thought to be due to an interaction between the developing pi bond, which occurs between these two carbons, and the carbonyl groups, so the carbonyl groups for our aldehyde here, and even though I didn't put in the carbonyls, we know that these red spheres here symbolize those aldehydes, and so there's an interaction between the developing pi bond and those carbonyls, which stabilizes the dienophile approaching in this way, and that gives us our aldehydes down in space.

事實證明，內向產物在大多數情況下都是首選產物，這就是所謂的內向規則，或榿木內向規則，它被認為是由於正在形成的π鍵（發生在這兩個碳和羰基之間）和羰基（我們這裡醛的羰基）之間的相互作用造成的、雖然我沒有寫入羰基，但我們知道這些紅色的球體象徵著這些醛，是以正在形成的π鍵和這些羰基之間存在相互作用，從而以這種方式穩定了親二烯烴的方式，這就產生了我們空間中的醛。

That gives us our endo product, so the endo product is preferred.

這樣我們就有了內臟產品，所以內臟產品是首選。

With the exo product, these carbonyls, these aldehydes would be way out here.

有了外顯子產物，這些羰基、醛類物質就會出現在這裡。

That's too far away from the developing pi bonds.

There's no interaction, so the exo product is not preferred.

沒有互動，所以外顯子產品不是首選。

On the left is our diene, on the right is our dienophile, and let's draw the product without stereochemistry again, so we move our six pi electrons, so we form a bond between those two carbons, we form a bond between these two carbons, and these pi electrons move down, so if we draw in our product, again, not worrying about stereochemistry, we'd have our aldehyde coming off of this carbon, we'd have a methyl group here and a methyl group here.

左邊是我們的二烯，右邊是我們的親二烯，讓我們在不考慮立體化學的情況下再次繪製產物，是以我們移動六個 pi 電子，在這兩個碳之間形成一個鍵，在這兩個碳之間形成一個鍵，這些 pi 電子向下移動，是以如果我們繪製我們的產物，再次不考慮立體化學，我們的醛將從這個碳上產生，我們將在這裡有一個甲基，在這裡有一個甲基。

Following our electrons, electrons in red, these pi electrons formed this bond.

在我們的電子（紅色電子）之後，這些π電子形成了這個鍵。

Our pi electrons in blue formed this bond, and our pi electrons in magenta moved down to here, so let's highlight those bonds on the model set, on the picture, so this bond in red formed between this carbon and this carbon, so formed in here, so there's that bond on our final product.

我們藍色的π電子形成了這個鍵，品紅色的π電子向下移動到了這裡，所以讓我們在模型集上、在圖片上突出顯示這些鍵，所以這個紅色的鍵在這個碳和這個碳之間形成，所以在這裡形成，所以我們的最終產品上就有了這個鍵。

The bond in blue formed between this carbon and this carbon, so here's that bond on our final product, but notice, if we draw the dienophile approaching this way, there is no stabilizing interaction between the developing pi bond and the carbonyl groups, so down here, I've flipped over the dienophile, so it has an endo approach to the diene, and now we think about our stereochemistry, so let's worry about the stereochemistry of our diene first.

藍色的鍵是在這個碳和這個碳之間形成的，所以這就是我們最終產品上的鍵，但注意，如果我們這樣繪製親二烯烴，在發展中的π鍵和羰基之間就沒有穩定的相互作用，所以在這裡，我把親二烯烴翻轉過來，讓它以內向的方式接近二烯，現在我們來考慮我們的立體化學，所以讓我們先擔心一下二烯的立體化學。

We know that inside substituents go up, so these two hydrogens, here they are on the diene, and in our product, those two hydrogens are going up in space, if we're looking down in this direction, so those methyl groups, so let me change colors here, so these two methyl groups, which I've used yellow in the model set, those two methyl groups go down, so down relative to those hydrogens going up, so those methyl groups are going down if we're staring down this direction, so let's draw that in for our product.

我們知道，裡面的取代基是向上的，所以這兩個氫，在這裡是在二烯上，在我們的產品中，這兩個氫在空間中是向上的，如果我們朝這個方向看的話，所以這些甲基，所以讓我在這裡改變顏色，所以這兩個甲基，我在模型組中用的是黃色，這兩個甲基是向下的，所以相對於那些向上的氫來說是向下的，所以如果我們朝這個方向看的話，這些甲基是向下的，所以讓我們畫出我們的產品。

We have our ring, so let's put in our double bond, and those methyl groups are going away from us, so we put those on a dash, so there's one methyl group and there's the other one.

我們有了我們的環，所以讓我們把雙鍵放進去，這些甲基要遠離我們，所以我們把它們放在破折號上，這樣就有了一個甲基和另一個甲基。

Next, let's think about the dienophile, so here is our dienophile, and if I draw a line here, we know the stuff to the left ends up down, so this aldehyde is going to be down in space, so let's follow that aldehyde through, so here is the aldehyde.

接下來，讓我們來考慮一下親二烯，這裡就是我們的親二烯，如果我在這裡畫一條線，我們知道左邊的東西最終會向下，所以這個醛在空間中會向下，讓我們跟著這個醛走，這裡就是醛。

We know that this endo approach gives us some stabilization between the developing pi bond and our carbonyl, so for our product, here is the aldehyde, and again, if we're looking down, this aldehyde is going away from us in space, so we'd have to put that aldehyde on a dash, so here is the aldehyde going away from us in space.

我們知道，這種內切法能使正在形成的 pi 鍵和我們的羰基之間具有一定的穩定性，所以對於我們的產物來說，這裡是醛，同樣，如果我們向下看，這個醛在空間中會遠離我們，所以我們必須把這個醛放在破折號上，所以這裡是在空間中遠離我們的醛。

What if the dienophile approached this way?

Well, this is still an endo approach, because here would be our aldehyde, and our developing pi bond would be back here, so there's a stabilizing interaction, so here's the aldehyde in our product, and if we're staring down this way, this aldehyde is going away from us in space, so let's draw this product.

這仍然是一種內切法，因為這裡是我們的醛，而我們正在形成的 pi 鍵在後面，所以這裡有一個穩定的相互作用，所以這裡是我們產物中的醛，如果我們朝下看，這個醛在空間中會遠離我們，所以讓我們畫出這個產物。

We would have our ring, we would have our double bond, and our aldehyde's going away from us at this carbon, so we put that aldehyde on a dash, and our methyl groups are still going away from us, so this one's going down, and this one's going down, so we draw in our methyl groups.

我們會有環，我們會有雙鍵，我們的醛會從這個碳處離開，所以我們把醛放在破折號上，我們的甲基仍然會離開我們，所以這個會向下，這個會向下，所以我們畫出我們的甲基。

What is the relationship between these two molecules?

Well, they are enantiomers of each other, so you should get a pair of enantiomers.

它們互為對映體，所以應該得到一對對映體。