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So we like to know if there are double bonds in our food molecules
因此我們希望知道食物分子中是否具有雙鍵
but how is that determined?
但如何知道呢
So this is what a "happy" carbon hydrogen molecule looks like
一個非常"開心"的碳氫化合物分子是這樣的
but in some cases there are not enough hydrogen atoms
但有時，氫原子數(shù)目不足
and the carbon will have to double bond with another carbon to share electrons
碳于是會同另一個碳之間形成雙鍵
This molecule
這個分子
is more reactive than this one
比這個分子反應(yīng)性更強
because a carbon-carbon double bond
因為碳碳雙鍵
is not as stable as a carbon-carbon single bond
沒有碳碳單鍵穩(wěn)定
Now let's watch as MIT's Dr. John Dolhun uses bromine
下面來看MIT的John Dolhun博士如何使用溴
to test for the presence of double bonds in a big slab of bacon
來測試一大塊培根中是否存在雙鍵
Here he is at the Cambridge Science Festival
這是他在劍橋科學(xué)節(jié)上的演示
I'm gonna turn on my burner here
我將打開我的燃燒器
OK, there we go
好了
So I'm gonna take my bacon
我夾起這塊培根
Basically shake it up a bit
放在里面搖一搖
You can see the red color of the bromine is going away
可以看到，紅色的溴消失了
So Dr. Dolhun heats up a piece of bacon
Dolhun博士先是給一塊培根加熱
and adds it to a flask filled with bromine
然后將它放入到充滿溴的燒瓶中
Bromine reacts with anything that has a carbon-carbon double bond
溴會同任何具有碳碳雙鍵的物質(zhì)反應(yīng)
This includes the acrolein that's produced when you cook bacon
包括加熱培根時生成的丙烯醛
which looks like this
丙烯醛是這樣的
as well as the unsaturated fat that's already present in the bacon
還包括培根中已經(jīng)存在的不飽和脂肪
Unsaturated fats are fat that have carbon-carbon double bonds
不飽和脂肪是具有碳碳雙鍵的脂肪
Fully saturated fats have no carbon-carbon double bonds
完全飽和脂肪是沒有碳碳雙鍵的脂肪
They're all carbon-carbon single bonds
其中全都是碳碳單鍵
and they're the ones that are bad for you
飽和脂肪對人危害較大
The breaking of the double bond looks like this
雙鍵的斷開是這樣的
We can tell that the reaction happens because the red color disappears
我們通過紅色的消失知道反應(yīng)發(fā)生
That's the bromine reacting with those carbon-carbon double bonds
這是溴同碳碳雙鍵的反應(yīng)
In our video recording of the experiment, it's hard to see the color change
實驗視頻錄制中，顏色變化比較難看清
So watch again very closely
所以請大家再仔細看一遍
Hope you enjoyed the video. I'll see you next time
但愿大家喜歡這個視頻，下次再見
