1) C3H7Cl There are just two isomers, not four: 1-chloro and 2-chloropropane.
2) C3H6Cl2 There are four structural isomers, not five: 1,1-, 1,2-, 2,2-, and 1,3-dichloropropane.
3) C3H5Cl3 1,1,1-, 1,1,2-, 1,2,2-, 1,1,3-, and 1,2,3-trichloropropane.
4) C4H10 Butane and 2-methylpropane.
These are good practice! The idea is to draw as many different structures as you can, without repeats. Good practice using the naming rules too. If two names turn out the same, then those were the same structure, not different ones. Sometimes you can't be sure until you compare the names.
5) C4H8Cl2 This one has the most structural isomers, nine. Start with the carbons in the regular straight chain, C–C–C–C, and attach the two chlorines: 1,1-, 1,2-, 1,3-, 1,4-, 2,2-, and 2,3-dichlorobutane. Then try an alternate carbon chain, three carbon main chain and the fourth carbon bonded to the middle carbon, and see how many ways you can attach the two chlorines (only three more ways).
8) As written, CH2Cl2 has only one structure. It probably should be C2H2Cl2. This is an alkene with three isomers total, two structural (1,1- and 1,2-dichloroethene) and then there are two geometric isomers of 1,2-dichloroethene, cis and trans.
Structural (or "constitutional") isomers have the same molecular formula but their atoms are connected in a different order, while geometric (or "stereo") isomers have their atoms connected in the same order, but their three-dimensional shapes (their molecular geometries) are still different. Cis and trans are examples of geometric isomers.
I won't deprive you of the fun of doing the rest of these, and once you get the hang of it after a little practice, you'll breeze through them, though it takes some time to draw 'em all! Hope this helps.
Steve
Free Forum Hosting
Important Announcement
First 