Final answer:
The acceptable structure for (R)-5-bromohept-2-yne is CH3-CH2-C≡C-CH(CH3)-CH2-Br which correctly reflects the placement of the alkyne and the bromine substituent, as well as the (R)-configuration at the chiral center.
Step-by-step explanation:
To determine the acceptable structure for (R)-5-bromohept-2-yne, we need to consider both the placement of the bromine atom and the configuration around the chiral center. The compound is an alkyne with seven carbon atoms (hept-) and a triple bond (yne) on the second carbon (2-). Additionally, a bromine substituent is located on the fifth carbon (5-bromo).
The correct structure must also match the (R)-configuration, which refers to the three-dimensional arrangement of the groups attached to the chiral center following the Cahn-Ingold-Prelog priority rules. In this case, the chiral center is the carbon bearing a methyl group (CH3) and two other different substituent groups.
With the given options, the correct structure for (R)-5-bromohept-2-yne is:
b) CH3-CH2-C≡C-CH(CH3)-CH2-Br
This structure has a triple bond between the second and third carbon atoms, a bromine atom on the fifth carbon, and a chiral center at the fourth carbon with the correct (R)-configuration.