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Ch.24 - The Chemistry of Life: Organic and Biological Chemistry

Chapter 24, Problem 40

Describe the intermediate that is thought to form in the addition of a hydrogen halide to an alkene, using cyclohexene as the alkene in your description.

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All right. Hello everyone. So this question is asking us to describe the intermediate found in the addition reaction of HBR to cyclops which is an ache. So recall first and foremost that our starting material is cyclops. This means that our parent chain is a five carbon ring. And because this molecule is an all keen, there is a double bond in between two carbon atoms inside of the ring. Recall also that when an keen is reacting with HBR, which is an example of a hydrogen Halide, that reaction is known as the hydro halogen of said akin. Now it's referred to as hydro halogen because the pi bond of the starting alkene is going to be broken. One of the carbons of the double bond receives a new bond to hydrogen, whereas the other receives a new bond to the halogen. In this case, Bromy. So lets go ahead and recall our steps here. First, the alkane and the hydrogen Halide here H pr are going to go ahead and combine with each other or rather react with each other in doing. So the electrons of the double bond are going to be used to establish a bond between carbon and hydrogen. And so the pi bond of the alkene is ultimately going to break, which means that it's no longer present in the structure of the intermediate and eventually the product. So here one of the carbons of the a keen is going to receive that new bond to hydrogen, but the other is going to be left electron deficient. This means that it's going to be depicted with a positive charge meeting our intermediate is a carbo cion. Now, our other product or other intermediate is the bromide ion because after the pi electrons of the akin removed the hydrogen from HBR, the electrons shared between hydrogen and bromine go towards bromine giving it a negative charge from here bromide or rather, the bromide ion is going to go ahead and attack the cruel cion by using one of its lone pairs of electrons to establish a bond between them. This results in the carbon atom that was initially positively charged. Now having a bond to Bromy. And from here, we have the description of our intermediate. Just thought I'd move this around just to open up some space. So our intermediate was the same five carbon chain from our starting material this time. However, with no double bond present in between carpets rather because the pi bond has since broken to establish a new bond between carbon and hydrogen. One of those carbons became neutral and the other ended up with a positive charge since it is now electron deficient. So as for the description, we can say that the intermediate has a positively charged carbon and therefore, it is known as a Kel K and there you have it. And so with that being said, thank you so very much for watching and I hope you found this helpful.