Monochloro substitution products (chemistry)


by Puchinita5
Tags: chemistry, monochloro, products, substitution
Puchinita5
Puchinita5 is offline
#1
Nov1-10, 05:35 PM
P: 162
1. The problem statement, all variables and given/known data

I uploaded a picture of a question in OWL. What I don't understand is, how to tell when I should take into account cis-trans products. For example, in the question I uploaded, why does chlorine add as cis and trans in right two images, but does not add cis and trans to the left two images (in the feedback section). I understand when enantiomers form, but I cannot seem to figure out when count for cis and trans. Any help would be appreciated!

2. Relevant equations



3. The attempt at a solution
Attached Thumbnails
screenshot17.jpeg  
Phys.Org News Partner Science news on Phys.org
Lemurs match scent of a friend to sound of her voice
Repeated self-healing now possible in composite materials
'Heartbleed' fix may slow Web performance
chemisttree
chemisttree is offline
#2
Nov2-10, 03:03 PM
Sci Advisor
HW Helper
PF Gold
chemisttree's Avatar
P: 3,725
If only I could show you a picture.... I'll try with words.

When you substitute the position adjacent the exo-methyl group, you generate TWO chiral centers... one at the chlorine position and the other at the methyl position. Before the substitution was made there were no chiral centers. Since you have two chiral centers, you can have both enantiomers and diastereomers. The cis/trans nomenclature refers to the position of the chlorine with respect to the methyl group when viewed along the somewhat puckered plane of the cyclobutyl ring. If both the chlorine and methyl are on the same side of the ring, that's cis. The opposite is true for trans. It really helps to build a model to see this.

When you substitute chlorine at the 3 position of the cyclobutane group, you don't generate any chirality (because, in this case, it is a meso compound) but the chlorine is either on the same side of the ring as the methyl or opposite, hence cis and trans.

In this contex, cis and trans do not refer to any particular mechanism (addition or substitution, for example) for the addition of chlorine. Rather, it refers to the position of the chlorine and the methyl group with respect to a particular face of the cyclobutyl group. Both on the same side is cis. One on each face is trans.


Register to reply

Related Discussions
Organic CHemistry: Improving existing products Biology, Chemistry & Other Homework 3
Chemistry and Food Products Chemistry 3
u substitution or substitution by parts? Calculus & Beyond Homework 8
Questions concerning cross products, dot products, and polar coordinates Introductory Physics Homework 1