[Fejimush]

I've been attempting to distill geranyl propionate C₁₃H₂₂O₂ at std pressure without much success. 

Prior to reaching the boiling temperature the solution begins to turn from a clear to yellow liquid.  It's at least 90% of pure prior to distillation.

I wonder if the ester is breaking down into an alkene and an alcohol prior to reaching the boiling point? 

If this is likely, what techniques can I use to avoid this?

Also, today I attempted a vacuum distillation.  The fluid is quite sensitive to temperature and will boil violently.

For reference, the bp of geranyl propionate at standard pressure is ~282°C.

Kindly,
Graham

[hairygorillaz]

I don't have experience with distilling esters, but I have distilled phosphines whose boiling points are around that of your compound without problems.

When you say it is sensitive to temperature, what do you mean? Do you mean it boils violently? If it is so, try vigourous stirring or boiling chips to prevent super boiling.

[discodermolide]

"Also, today I attempted a vacuum distillation.  The fluid is quite sensitive to temperature and will boil violently."

Never heard of a pressure/temperature nomogram? see http://www.sigmaaldrich.com/chemistry/solvents/learning-center/nomograph.html

Try applying the vacuum slowly, then the compound will not boil.

[AWK]

B.p. 128 C at 15 mm Hg (from Fenaroli's Handbook of Flavor Ingredients - GOOGLE books)

[Fejimush]

Thanks for the feedback and tips folks.  This is really helpful.

Never heard of a pressure/temperature nomogram? see http://www.sigmaaldrich.com/chemistry/solvents/learning-center/nomograph.html

Try applying the vacuum slowly, then the compound will not boil.

I didn't know that there were online predictive tools.   This is excellent.  Thanks much!

I've been away from o-chem for a long time and getting back into it. 

[Fejimush]

On this topic, do high bp esters tend to breakdown prior to reaching their bps? 

This is the first time I've experience this.  It seems odd for a chemical to have a bp that it can never achieve.

[AWK]

On this topic, do high bp esters tend to breakdown prior to reaching their bps? 

This is the first time I've experience this.  It seems odd for a chemical to have a bp that it can never achieve.

Geranyl propionate contains two isolated double bonds. They can be easily oxidized  or polymerized at boiling point.
I thing distillation under nitrogen or argon is adviced, even under reduced pressure.

[Fejimush]

Thanks AWK!

[Irlanur]

It seems odd for a chemical to have a bp that it can never achieve.

eehm... sugar?

[Fejimush]

It seems odd for a chemical to have a bp that it can never achieve.

eehm... sugar?

Thanks Irlanur! 

I've haven't worked with sugar outside of the kitchen at low temperatures.

[discodermolide]

On this topic, do high bp esters tend to breakdown prior to reaching their bps? 

This is the first time I've experience this.  It seems odd for a chemical to have a bp that it can never achieve.

Lots of compounds decompose before reaching their melting or boiling point.