Quick Organic Chem: P & Q Structural Formulas + Q to R Conversion

[new hand]

Homework Statement

______________Stgae 1 [/B]
P:C₃H₆O ----->
_________________Br2 in organic solvent
Q:C₃H₆OBr₂
Stage 2
-->R:C₃H₅Br₃
1.What is the structural formula of P and Q respectively?
2.What is the reagents in the conversion of Q to R??
(1) Phosphorous tribromide liquid
(2) Bromine liquid
(3) Solid Potassium bromide and concentrated sulphuric acid
Which one can??

The Attempt at a Solution

Are there two possible structures for P. One is 1,2-dibromopropenol and
2,3-dibromopropenol. My answer is 1,2-dibromopropenol.However someone told me that 2,3-dibromopropenol is the answer as Bromine atoms cannot add to carbon atom with hydroxyl group, whywhywhywhy??

I totally have no idea for question 2... lol

 

[Ygggdrasil]

Are you talking about structure of Q? P has no bromines, and it's useful to consider the possible structures of P before trying to figure out what Q might be.

You certainly can add bromine to an enol group. Here's a link you may find useful:
http://research.cm.utexas.edu/nbauld/teach/ch610bnotes/ch19.htm

 

[Janiceleong26]

Homework Statement

______________Stgae 1 [/B]
P:C₃H₆O ----->
_________________Br2 in organic solvent
Q:C₃H₆OBr₂
Stage 2
-->R:C₃H₅Br₃
1.What is the structural formula of P and Q respectively?
2.What is the reagents in the conversion of Q to R??
(1) Phosphorous tribromide liquid
(2) Bromine liquid
(3) Solid Potassium bromide and concentrated sulphuric acid
Which one can??

The Attempt at a Solution

Are there two possible structures for P. One is 1,2-dibromopropenol and
2,3-dibromopropenol. My answer is 1,2-dibromopropenol.However someone told me that 2,3-dibromopropenol is the answer as Bromine atoms cannot add to carbon atom with hydroxyl group, whywhywhywhy??

I totally have no idea for question 2... lol

Hi, first of all, what do you think P and Q are? And how did P become Q?

There are many ways for Q to become R, such as:
i) react P(s) + Br2 in situ
ii) NaBr (s) + h2so4 (conc), heat
iii) react with HBr (g), room temp. or HBr (aq) conc., heat

And about 1,2-dibromopropanol, are you regarding to Q I'm assuming you mean Q anyways. Well, it not only can be 1,2- , it can also be 1,1- , 2,2- . But think about 2,3- ...Isn't it the same with 1,2- ?? Since there are only 3 Carbons? Or do you mean why can't it be 1,2- bromopropan-1-ol instead of 1,2-bromopropan-3-ol?

May I know where did you get this question from? If can, can you show us a picture of the full question, it'll help a lot.

 

[Merlin3189]

I'm only a non-chemist with a casual interest, but can I make one suggestion?

For part 2, what do you think the other product of the reaction is?
ie. Q + part of reagent -> R + what?
Does that give you a clue to what the reagent must be?[Can I also just wonder why people are talking about "enols" ? I had assumed at first that it was just a mis-spelling (or foreign spelling) for propane or propanol?]- edited below
On second thoughts (after half an hour!) scrub this bit. I just assumed it was 1-propanal and did not think about other possibilities. Looking at the reaction, may be other candidates are more likely.

 

[Janiceleong26]

Homework Statement

______________Stgae 1 [/B]
P:C₃H₆O ----->
_________________Br2 in organic solvent
Q:C₃H₆OBr₂
Stage 2
-->R:C₃H₅Br₃
1.What is the structural formula of P and Q respectively?
2.What is the reagents in the conversion of Q to R??
(1) Phosphorous tribromide liquid
(2) Bromine liquid
(3) Solid Potassium bromide and concentrated sulphuric acid
Which one can??

The Attempt at a Solution

Are there two possible structures for P. One is 1,2-dibromopropenol and
2,3-dibromopropenol. My answer is 1,2-dibromopropenol.However someone told me that 2,3-dibromopropenol is the answer as Bromine atoms cannot add to carbon atom with hydroxyl group, whywhywhywhy??

I totally have no idea for question 2... lol

Homework Statement

______________Stgae 1 [/B]
P:C₃H₆O ----->
_________________Br2 in organic solvent
Q:C₃H₆OBr₂
Stage 2
-->R:C₃H₅Br₃
1.What is the structural formula of P and Q respectively?
2.What is the reagents in the conversion of Q to R??
(1) Phosphorous tribromide liquid
(2) Bromine liquid
(3) Solid Potassium bromide and concentrated sulphuric acid
Which one can??

The Attempt at a Solution

Are there two possible structures for P. One is 1,2-dibromopropenol and
2,3-dibromopropenol. My answer is 1,2-dibromopropenol.However someone told me that 2,3-dibromopropenol is the answer as Bromine atoms cannot add to carbon atom with hydroxyl group, whywhywhywhy??

I totally have no idea for question 2... lol

Hi, do you understand my explanations? Please reply to us thanks.

 

[StoneBurner]

I'm only a non-chemist with a casual interest, but can I make one suggestion?

For part 2, what do you think the other product of the reaction is?
ie. Q + part of reagent -> R + what?
Does that give you a clue to what the reagent must be?[Can I also just wonder why people are talking about "enols" ? I had assumed at first that it was just a mis-spelling (or foreign spelling) for propane or propanol?]- edited below
On second thoughts (after half an hour!) scrub this bit. I just assumed it was 1-propanal and did not think about other possibilities. Looking at the reaction, may be other candidates are more likely.

"enol" is a chemical term.

 

[Merlin3189]

"enol" is a chemical term.

Yes I did look it up (though I'm not sure I understood what I found!)
I was originally puzzled because it had sounded to me like an alcohol based on an alkene, whereas the original substance looked to me like an aldehyde of an alkane (propanaldehyde?).
I did go back and edit my post when I realized that there were more complex possibilities, including a C=C, but left my original comment in brackets so as not to confuse anyone who had read it in the meantime. Now, of course, I wish I'd not said it, as it is irrelevant to the OP question.

I'm sorry the thread has dried up, as I would have liked to know what the real answer is! I thought at first you could only solve it if you guessed the original compound correctly, but now I wonder if you have to work backwards from the Q and R ?
I am positioning the Cl 's on the basis that they are very electrophillic and will go where electrons are most available (a bit of naive physics!) This would not prevent them going on the C with the O, but since O is also electrophillic, that C would be short of electrons so they would be less likely to go there.