Lion Indicate whether the use of wedge and dash bonds are required when drawing the product of using: 1-methylcyclohexene as your starting material with: A) hydroboration-oxidation yes no B) hydrogenation with a metal catalyst using protium yes no C) hydrogenation with a metal catalyst using deuterium yes no D) free radical addition of HBr yes no E) vicinal dihalide formation yes no F) electrophilic addition of HX yes no G) vicinal halohydrin formation yes no H) hydration via electrophilic addition under aqueous acid conditions yes no
Lion Indicate whether the use of wedge and dash bonds are required when drawing the product of using: 1-methylcyclohexene as your starting material with: A) hydroboration-oxidation yes no B) hydrogenation with a metal catalyst using protium yes no C) hydrogenation with a metal catalyst using deuterium yes no D) free radical addition of HBr yes no E) vicinal dihalide formation yes no F) electrophilic addition of HX yes no G) vicinal halohydrin formation yes no H) hydration via electrophilic addition under aqueous acid conditions yes no
The Correct Answer and Explanation is:
Here are the correct answers to whether wedge and dash bonds are required when drawing the product formed from 1-methylcyclohexene under the following reactions:
| Reaction | Wedge/Dash Required? |
|---|---|
| A) Hydroboration-oxidation | Yes |
| B) Hydrogenation with H₂ and metal catalyst | Yes |
| C) Hydrogenation with D₂ and metal catalyst | Yes |
| D) Free radical addition of HBr | No |
| E) Vicinal dihalide formation | Yes |
| F) Electrophilic addition of HX | No |
| G) Vicinal halohydrin formation | Yes |
| H) Hydration via aqueous acid (electrophilic addition) | No |
Explanation
The use of wedge and dash bonds in organic chemistry is crucial when a reaction produces stereocenters—carbon atoms with four different groups attached—because the three-dimensional (3D) spatial arrangement of atoms becomes relevant.
A) Hydroboration-oxidation occurs via syn addition of H and OH across the double bond, forming a new stereocenter. Since the OH and H add to the same face of the molecule, wedge/dash bonds are required to show this stereochemistry.
B) Hydrogenation with H₂ and a metal catalyst also proceeds via syn addition of hydrogens, potentially generating stereocenters. Therefore, wedge/dash notation is necessary to indicate which face of the ring the hydrogens added to.
C) Hydrogenation with D₂ behaves identically to B, except deuterium (D) is used. Because D and H are distinguishable, stereochemistry is even more important, and wedge/dash bonds are required.
D) Free radical addition of HBr leads to non-stereoselective radical intermediates and planar carbocation-like species. The product is often a mixture of racemic or non-stereospecific products. Thus, wedge/dash bonds are not required.
E) Vicinal dihalide formation (e.g., Br₂ addition) is anti-addition, where halogens add to opposite faces of the double bond, creating stereocenters. Wedge/dash bonds are required to represent the anti configuration.
F) Electrophilic addition of HX leads to a planar carbocation intermediate, so the resulting product does not have a fixed stereochemistry at the new center; wedge/dash is not required.
G) Vicinal halohydrin formation is anti-addition of OH and X (e.g., Br), resulting in stereocenters. Wedge/dash bonds are needed to show this stereochemistry.
H) Acid-catalyzed hydration involves a planar carbocation intermediate and does not control stereochemistry at the new center, so wedge/dash notation is not required.
