Consider the molecule 1-bromopropane. Looking down C1-C2, draw Newman projections of a. the anti conformation b. the gauche conformation Br 5×2 H 3 Br CH₃
The Correct Answer and Explanation is :
To draw the Newman projections of 1-bromopropane looking down the C1-C2 bond, we consider two different conformations: the anti conformation and the gauche conformation. Here’s a step-by-step explanation and description of what each of these conformations would look like in a Newman projection.
Anti Conformation
In the anti conformation, the substituents on the front and back carbons are positioned 180 degrees relative to each other. For 1-bromopropane looking down the C1-C2 axis:
- The front carbon (C1) will have the bromine atom and two hydrogens. In the Newman projection, bromine is drawn larger due to its larger atomic size.
- The back carbon (C2) will have the methyl group (CH₃) and two hydrogens.
- In the anti conformation, the bromine atom on C1 and the methyl group on C2 are directly opposite each other (180 degrees apart).
Gauche Conformation
In the gauche conformation, the key substituents are positioned approximately 60 degrees apart:
- As in the anti conformation, C1 has the bromine and two hydrogens, and C2 has the methyl group and two hydrogens.
- However, in this gauche conformation, the bromine on C1 and the methyl group on C2 are not directly opposite but rather offset by about 60 degrees.
For visualization, I will generate two images for these Newman projections:
- Anti Conformation: Newman projection of 1-bromopropane with Br on C1 and CH₃ on C2 directly opposite each other.
- Gauche Conformation: Newman projection of 1-bromopropane with Br on C1 and CH₃ on C2 offset by about 60 degrees.
Let’s create these images now.
Here are the Newman projections for 1-bromopropane:
- Anti Conformation: This conformation shows the bromine on the front carbon (C1) and the methyl group on the back carbon (C2) directly opposite each other, representing a 180-degree separation.
- Gauche Conformation: In this image, the bromine on the front carbon (C1) and the methyl group on the back carbon (C2) are offset by about 60 degrees, indicating the gauche relationship between these groups.
These images visually depict how the atoms and groups are arranged relative to each other in space when viewed along the C1-C2 bond axis of 1-bromopropane in different rotational conformations.
