[patchface]

I learned about FT-IR spectra interpretation back in the day but never became proficient at it. I didn't know if any FT-IR experts wanted to help me out.

I ran a yellow-transparent grease like material in my lab and am definitely not getting any leads via my reference database.

I am trying to figure out what is going on mainly between 1200 and 1700 wavenumbers..

I was thinking some Carboxylic acid or amide group action but not sure.

Thank you.

[Corribus]

The C-H stretching region looks a lot like polypropylene to my eye- certainly it is representative of a hydrocarbon that has a good mix of both CH2 and CH3 groups (i.e., something highly branched or relatively short chain). You can compare it to the spectrum of polyethylene which mostly just has two sharp peaks owing to almost all C's being CH2. The sharp peaks all occur below 1600 wavenumbers, which except in some unusual circumstances rules out most carbonyls. Amides are pretty low as far as carbonyls go but not below 1600 cm-1 typically. Plus I'm not sure what grease would have an amide group. The sharp peaks below 1600 cm-1 are consistent with scissoring and other bending modes of CH2 and CH3 groups, which would be plentiful in a grease, although they're not often so close to 1600 cm-1 (usually more in the 1400-1500 cm region). 1500-1600 is the right region of aromatic ring stretches. 

I'm guessing the noisy region below 1000 cm-1 is just poor absorptivity of your instrument? This region would have most of your low frequency aliphatic rocking motions.

What kind of grease is it? Definitely not a silicon-based grease, due to total absence of Si-H stretches.

[patchface]

Thank you very much for your input.

It is a substance that was plugging a diesel fuel filter. It just happens to have a grease like texture. Doesn't appear to be soluable in pentane and sort of in isopropyl alcohol.

We think the substance has something to do with the fuel additives (being over added or added inproperly). I suppose fuel additives opens the door to all sorts of functional groups. I was hoping it was one major additive compound causing the issue that would stand out.

The aromatic stretching is interesting. That could possibly narrow it down.

[patchface]

not obviously soluable in toluene or methylene chloride

[patchface]

Looks like some of the peaks could be COO-  bonds as I see that they show up just below 1600 and above 1400.