[shrikantvarma]

How to prepare cyclopentadiene in laboratory from its dimer,what are the properties of it ?

[discodermolide]

You need to distill it at high temperature and trap the distillate at low temperature, -78°C or lower or trap it with another dieneophile. You could trap it into liqud N2. nThis won't be easy.

[stevet]

If I'm not mistaken, Organic Syntheses has a really good procedure for this reaction. Just search for it, and it gives you all the detail, including hazards etc. I had it for one of my projects, but not sure where it is now, so can't give the exact reference.

[OC pro]

Here you go with the link:

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0238

The set-up is quite easy. You don´t have to cool the trap to -78°C, ice will also do the job. You should use the fresh distilled cyclopentadiene immediately.

[ardbeg]

it smells delightful.  beware.

[jchan123]

As you know, you'll be essentially performing a retro Diels-Alder reaction so if you let your freshly distilled cyclopentadiene (CP) sit around for too long it will re-dimerize.  Just to let you know I've kept CP at -20 oC for over two weeks and only 10% re-dimerizes. So you do have a bit of time and don't necessarily need to use it immediately.

Jeff