[noobie]

1-chloro-1-pentene
1-heptene
1,2-dimethylcyclopentene
2-methyl-3-hexene
2-methyl-2-butene
1-methylcyclopentane
1,2-dimethylcyclohexane

here's what i got:
1-chloro-1-pentene - yes
1-heptene - no
1,2-dimethylcyclopentene - Yes
2-methyl-3-hexene - yes
2-methyl-2-butene - Yes
1-methylcyclopentane -Yes
1,2-dimethylcyclohexane  - No

but my answer doesn't seem to be correct. please help

[Alpha-Omega]

In order to make such a determination for each of your species you will have to draw it out.  I am attaching a link that explains stereoisomerism/geometric isomers and how to make that determination.

http://www.chemguide.co.uk/basicorg/isomerism/geometric.html

http://www.usm.maine.edu/~newton/Chy251_253/Lectures/Geometric%20Isomers/GeometricIsomers.html

Creative chemistry molecular models:


http://www.creative-chemistry.org.uk/molecules/geometrical.htm

[noobie]

Thanks for the reply.
I did draw them out and i also looked them up online. Here are the ones that i found online:
1-chloro-1-pentene - can't find a image online
1 heptene: http://pubchem.ncbi.nlm.nih.gov/image/imgsrv.fcgi?t=l&cid=11610
1,2-dimethylcyclopentene http://www.cheric.org/research/kdb/hcprop/molimg/619.gif
2-methyl-3-hexene http://sci-toys.com/scichem/cid_images/cid_5352548.png
2-methyl-2-butene http://mits.nims.go.jp/matnavi/monomer/01/M0101070.png
1-methylcyclopentane http://www.orgsyn.org/orgsyn/cdxgif/CV8P0377.gif
1,2-dimethylcyclohexane http://people.uis.edu/gtram1/organic/alkanes/dimec6-3.gif

here are the answers i can up with now:
1-chloro-1-pentene - yes because the cholorine can be up or down giving us cis or trans
1-heptene - no because either way it's a heptene
1,2-dimethylcyclopentene - no
2-methyl-3-hexene - yes
2-methyl-2-butene - no because of double bond
1-methylcyclopentane - yes
1,2-dimethylcyclohexane - yes

please verify these answers because this homework is worth alot of points

[sjb]

here are the answers i can up with now:
1-chloro-1-pentene - yes because the cholorine can be up or down giving us cis or trans
1-heptene - no because either way it's a heptene
1,2-dimethylcyclopentene - no
2-methyl-3-hexene - yes
2-methyl-2-butene - no because of double bond
1-methylcyclopentane - yes
1,2-dimethylcyclohexane - yes

please verify these answers because this homework is worth alot of points

Interesting reasoning. Why do you feel 1,2-dimethylcyclopentene does not exist as cis / trans, but 1,2-dimethylcyclohexane does? Why should a heptene not exhibit such isomerism?

Consider http://en.wikipedia.org/w/index.php?title=Cis-trans_isomerism&oldid=206671949 as a guide

[noobie]

i thought that the heptene would because it can be in the chair formation. i also found http://people.uis.edu/gtram1/organic/alkanes/dimec6-3.gif&imgrefurl=http://people.uis.edu/gtram1/organic/alkanes/cyclicalkanes.htm&h=213&w=512&sz=5&hl=en&start=1&um=1&tbnid=V1eAH3OTtv8TJM:&tbnh=54&tbnw=131&prev=/images%3Fq%3D1,2-dimethylcyclohexane%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN which shows me images of cis and trans 1,2-dimethylcyclohexene. so there can be a cis or trans for 1,2-dimethylcyclopenete too? can you please tell me which ones are wrong?

[noobie]

okay. here are my latest answers:

1-chloro-1-pentene - yes
1-heptene -No
1,2-dimethylcyclopentene - Yes
2-methyl-3-hexene -Yes
2-methyl-2-butene -NO
1-methylcyclopentane -No
1,2-dimethylcyclohexane -Yes

please tell me if any of them are incorrect

[sjb]

These all seem fine to me.

[Alpha-Omega]

Soory,  Has been awhile since I checked reponses...Yeah they look great...and looks like you are on your way to understanding a little/A lot about symmetry operations; and, determining stereoisomers/geometric isomers.  Good Job!!!!