[samta]

A few quesitions, all answers appreciated!

Is this okt-2,4,6-trien?:
http://i.imgur.com/g9Uxr.png

How does conjugated hydrocarbons cause isomerism?
How can I see how many (theoretical) stereoisomers of okt-2,4,6-trien exist?

[discodermolide]

The name looks OK.
Isomerism in alkenes is deals with isomers about the C=C. You can have trans isomers as you drew, or cis isomers where both substituents are on the same side of the olefin.
see picture.
The trans isomers are also known  E (from the German entgegen = apart) and the cis isomers as Z (from the German zusammen = together.

[samta]

Thanks!

[A_V_B]

Only 6:
ZZZ
EEE
ZZE
EEZ
ZEZ
EZE.

[curiouscat]

Only 6:
ZZZ
EEE
ZZE
EEZ
ZEZ
EZE.

Would all of these be stable or do they freely interconvert? i.e. Can I isolate, say, EZE oct-2,4,6-triene and keep it in a bottle?

[discodermolide]

They are stable except maybe towards light.
They can only freely convert if you break and re-form a double bond.