Draw the stereoisomeric products for the following reaction. HC HO -CH? products + Br? 1st attempt See page 662 6 OF 12 QUESTIONS COMPLETED < 08/12 > SUBMIT ANSWER
The Correct Answer and Explanation is:
To accurately draw and explain the stereoisomeric products of the reaction, I need to clarify a few things in your question. Your description:
“HC HO -CH? products + Br?…”
appears to be a partial or unclear representation of the chemical reaction. However, based on common textbook problems and the reference to Br₂ (bromine) and possibly an alkene or alkyne reacting with it, I will interpret the question as referring to the bromination of an alkene in aqueous solution, such as the reaction of cis-2-butene or trans-2-butene with Br₂ in water or an organic solvent.
Let me reconstruct the likely scenario:
Interpreted Reaction:
An alkene reacts with Br₂, leading to stereoisomeric dibrominated products.
Example:
CH₃–CH=CH–CH₃ (2-butene) + Br₂ → Products
Answer:
When Br₂ reacts with an alkene (like 2-butene), it adds across the double bond anti (i.e., on opposite faces), forming a vicinal dibromide (two Br atoms on adjacent carbon atoms). Because this reaction creates two chiral centers, the product can exist as stereoisomers.
For 2-butene, the stereoisomers of the product 2,3-dibromobutane are:
- (2R,3R)-2,3-dibromobutane
- (2S,3S)-2,3-dibromobutane
- (2R,3S)-2,3-dibromobutane (meso)
- (2S,3R)-2,3-dibromobutane (meso)
The meso compound is achiral due to an internal mirror plane, while the others are enantiomers (non-superimposable mirror images).
Explanation
The bromination of an alkene is a classic example of an electrophilic addition reaction that proceeds via a three-membered bromonium ion intermediate. When a molecule like 2-butene reacts with Br₂, the double bond (π electrons) attacks a Br₂ molecule, temporarily forming a bromonium ion — a positively charged, bridged intermediate.
This bromonium ion is then attacked by a bromide ion (Br⁻) from the backside, opening the ring in a process called anti addition. This stereospecific anti addition leads to two different Br atoms attaching to adjacent carbon atoms on opposite faces of the former double bond.
Because this process introduces two new stereocenters, the products can exist in multiple stereoisomeric forms:
- If both Br atoms are on the same side, it is the meso compound (optically inactive due to internal symmetry).
- If the Br atoms are on opposite sides in different configurations, the product is a pair of enantiomers (optically active).
Thus, three stereoisomeric products are possible:
- A pair of enantiomers: (2R,3R) and (2S,3S).
- A meso compound: (2R,3S) or (2S,3R).
This reaction highlights the importance of stereochemistry in organic chemistry and how reaction mechanisms influence the 3D structure of products.
