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

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Discussion Overview

The discussion revolves around the structural formulas of organic compounds P and Q, specifically C3H6O and C3H6OBr2, and the reagents required for the conversion of Q to R (C3H5Br3). Participants explore the possible structures for P and Q, as well as the appropriate reagents for the conversion process.

Discussion Character

  • Homework-related
  • Debate/contested
  • Exploratory

Main Points Raised

  • Some participants propose that P could be either 1,2-dibromopropenol or 2,3-dibromopropenol, while others assert that bromine cannot add to a carbon atom with a hydroxyl group.
  • One participant suggests that understanding the structure of P is crucial before determining the structure of Q.
  • There are multiple proposed methods for converting Q to R, including the use of phosphorous tribromide, bromine, or potassium bromide with concentrated sulfuric acid.
  • Questions arise about the nature of enols and their relevance to the discussion, with some participants expressing confusion about the term.
  • One participant reflects on the possibility of needing to work backwards from Q and R to deduce the original compound P.

Areas of Agreement / Disagreement

Participants express differing opinions on the structural formulas of P and Q, with no consensus reached on which structures are correct. The discussion remains unresolved regarding the appropriate reagents for the conversion of Q to R.

Contextual Notes

Some participants note the complexity of the problem and the potential for multiple interpretations of the structures involved. There is uncertainty about the definitions and implications of terms like "enol," which may affect the understanding of the reactions discussed.

new hand
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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
 
Last edited:
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new hand said:

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.
 
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.
 
Last edited:
new hand said:

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
new hand said:

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.
 
Merlin3189 said:
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.
 
StoneBurner said:
"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.
 

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