[organicidiot]

What reactants would you react with butyl-benzene to get a chlorine on the first and second carbon of the butane closest to the benzene ring?(sorry not sure what name would be) benzene-1,2dichlorobutane maybe. Haven't really learned naming aromatic compounds this complex yet. Please explain how you came to the conclusion you did.

1.Br2, light, heat 2.NaOCH2CH3, heat 3. Cl2
2.Br2, light, heat 2.NaOCH2CH3, heat 3. HCl
3.Br2, light, heat 2.NaNH2 (2 moles), NH3 3. HCl (2 moles)
4.Br2, light, heat 2.NaNH2 (2 moles), NH3 3. Cl2 (1 mole)
5.Br2, light, heat 2.NaNH2 (2 moles), NH3 3. NaCl (2 moles)

Any direction or help would be much appreciated.  Thanks.

[sjb]

OK, lets take this one stage at a time.

In all your proposed conditions, you start by adding Br₂ with light and heat. What does this do?

[organicidiot]

Ok, I am quite lost on this particular question, but I believe that bromination of the butyl substituent will occur.  I am guessing that a free radical halogenation occurs with the heat/light inciting that reaction to occur. I assume that bromination will occur at the two carbons closest to the benzene. But I could be wrong on that. If it occurred only at one carbon, I would say that bromination would occur at the second carbon.

[Squirmy]

  I am guessing that a free radical halogenation occurs with the heat/light inciting that reaction to occur.

yes

I assume that bromination will occur at the two carbons closest to the benzene.

I'm guessing this assumption is based on the product, which has chlorine atoms on the two carbons closest to the benzene. It helps to be flexible in organic...rather than thinking from starting material to final product, do you know of any reactions that could lead to a product with chlorines attached to adjacent carbons?

But I could be wrong on that. If it occurred only at one carbon, I would say that bromination would occur at the second carbon.

If you have more than one carbon where bromination can occur, how can you predict where it will occur?

[organicidiot]

I sort of have two theories.
1st theory: The answer is A. After bromination occurs. (Bromine would only be added to one of the carbons,I guess it would bond to the the second carbon from the benzene, and the first carbon would lose a hydrogen, leaving a double bond between the two,  then chlorination would occur.
WHY I'M NOT SURE: I thought NaOCH2CH3 usually needed ethanol for a reaction to occur. 

2nd theory:the answer is C.  bromination occurs, leaving a dihalide. Then dehydrohalogention would occur. I have seen  NaNH2 used in liquid ammonia before, as a strong base, which  would remove the bromine atoms and hydrogens, leaving a triple bond between the first and second carbon closest to the benzene.  Then hyrdohalogenation would occur with the HCl (2 moles)

I am leaning toward C as my answer Overall since I don't have as many reservations about choosing that one

[Squirmy]

Adding excess HCl to an alkyne does add 2 chlorines to a molecule, but do the Cl's end up on adjacent carbons?

You're very close with your first theory...the only thing wrong is where the bromination occurs. In the mechanism for radical bromination, a hydrogen atom is removed to form a carbon radical.

Compare the radicals that could form from butylbenzene. One is more stable than the rest and leads to the major product.

[organicidiot]

what about NaOCH2CH3 needing ethanol (or any alcohol) for the reaction to proceed? That it totally throwing me off as to why my first theory is the correct one.

[Squirmy]

Why do you think ethanol is necessary for the reaction to occur?

The EtOH is usually found with NaOEt because NaOEt is made by mixing EtOH with a base like NaH, and just acts as solvent.

The key is that you have an alkyl halide, a strong base/nucleophile and heat  E2 reaction. The only other possibility would be SN2, but heating typically favors the elimination product.

[organicidiot]

Ok, in regards to which carbon the bromine(s) would bond too. I know that Bromine is selective in terms of which carbon it would bond to.  Bromine would prefer a tertiary carbon to a secondary carbon for example. I guess it would bond to the first carbon.

[Squirmy]

Yes, the bromine attaches to the carbon adjacent to the ring.

Why do you think that is? What makes a radical at that position more stable than one on the next carbon or the next? All are secondary, so it must be something else.

[organicidiot]

because it is a benzylic radical. It is more stable than even a tertiary carbon because of delocalization of the radical into the benzene ring. Right?

[Squirmy]

Yep...exactly

[Rishi]

I would suggest you to make Butyrophenone and then convert it to the corresponding alcohol. Dehyration of the same will result in the double bond between the first and second carbon from the benzene ring. You can then readily halogenate the double bond with Bromine to get the dihalo derivative.
I hope this works out.

[sjb]

I would suggest you to make Butyrophenone and then convert it to the corresponding alcohol. Dehyration of the same will result in the double bond between the first and second carbon from the benzene ring. You can then readily halogenate the double bond with Bromine to get the dihalo derivative.
I hope this works out.

All well and good, but this seems to be chemistry en papier, where we have some choices, and need to choose between them, rather than develop a new route.