There have been many such studies of the absorption of I2 in solvents, both polar and nonpolar, going back to the 1950s and earlier. Not sure about a ref for hexane right now, but my students and I published results for heptane and CCl4 a few years back and reviewed a lot of the literature, so you might find this a good place to start -- J Phys. Chem A. 105, p 11183 (2001).

There have been many such studies of the absorption of I2 in solvents, both polar and nonpolar, going back to the 1950s and earlier. Not sure about a ref for hexane right now, but my students and I published results for heptane and CCl4 a few years back and reviewed a lot of the literature, so you might find this a good place to start -- J Phys. Chem A. 105, p 11183 (2001).

This was exactly the information i needed. Thank you very much for your time!

Perhaps the solvents should be dry. H2O could couple with I2 and distort the spectrum. Could be important at low I2 levels???

The spectrum is indeed quite different for polar solvents, but you don't have to worry about very small water contamination of the nonpolar ones: In any event, spec-pure forms of the common nonpolar solvents are not terribly expensive

OK but if one is extracting trace I2 from aqueous media then the effect could be significant. It is my engineer persona thinking " that's a good idea - what is wrong with it?"

In polar solvents the spectrum is shifted, but its intensity is not altered much. Thus, if the I2 has been extracted from, say, water into a nonpolar solvent like hexane (where its solubility is much greater), it seems unlikely to me that the residual water in the hexane (which must be very small) can significantly affect that spectrum.

Hi Deniz Bozyigit,

One reason that you could not have found a reference about the absorption of iodine molecules is simply because the absorption depends on the nature of the solvent. You specifically want the absorption of iodine in hexane which is not an easy piece of information to find in many areas in science. It would be a golden opportunity for you to provide such reference. Do not wait for someone to do it for you. Waste no time and take the initiative to be the first. While you at it, if you can, you can do absorption of iodine molecule in different non polar solvents which are not very popular in literature. I am not too sure how can these information ties in with the work that you are doing right now. It would be ludicrous scientific journal to publish a list of absorption of iodine molecule in so many non polar solvents. Alternatively you can publish a review article on the absorption of iodine molecule and its related area from different journals and add your own list of absorption. The reader would find it more interesting and useful to read.

I hope that I was helpful,

Yours sincerely,

Ali Al-Saadi

Hello Ali,

thank you very much for your answer. I'm an electrical engineer by training and in the process to build solar cells - so chemistry and spectroscopy is not exactly my strong suit. I'm very happy that others - like Mr. Joel Tellinghuisen - use their expertise to work on these topics!

Best regards,

Deniz Bozyigit

Hello Ali

I worked with iodine vapour and the absorption spectrum can be found in 64. Utilization of iodine in the enhancement of the efficiency of flat plate collectors.

Solar Energy, 34 (1985) 289.

The spectrum in nonpolar solvents should not vary from that of the vapour.

Regards

Mahmood M. Barbooti, Ph. D/

Dear Deniz

From your remarks I noticed that you are involved in some solar energy storage program. Can we move forward by utilizing the results in my 1985 article in some new installations to prove the applicability of our findings/ Thank for Ali to initiate this conversation...Regards

Mahmood

I am rather puzzled because molecualr iodine was and is the classical compound in educating spectroscopy in undergraduate class, becasue it shows such nice fine structure in the visible range that can be explained by its vibrational/rotational constants.

In an article from 1949 the spectra are provided in various non-polar solvent in whihc the fine structure is absent due to line-broadening by relaxation. I bet the spectrum in hexane is almost identical to that in benzene.

ref

https://www.google.nl/#hl=en&gs_rn=12&gs_ri=psy-ab&pq=rotational%20vibronic%20iodine%20absorption%20spectrum&cp=27&gs_id=66&xhr=t&q=iodine+absorption+spectrum+dissolved&es_nrs=true&pf=p&sclient=psy-ab&oq=iodine+absorption+spectrum+dissolved+&gs_l=&pbx=1&bav=on.2,or.r_qf.&bvm=bv.46340616,d.d2k&fp=b42f9ac95e687697&biw=1366&bih=559

Harry, your answer is not quite correct. While it is true that there is no fine structure (rotational or vibrational) in solution, there is a big difference between aromatics like benzene and other nonpolar solvents: Aromatics form charge-transfer complexes with strong absorption in the near-UV. This was, in fact, probably the topic of your 1949 paper ... if it was by by Benesi and Hildebrand -- the paper that largely started the study of such weak complexes. It is generally much less appreciated that there are also changes in the spectrum in the visible region, making the visible spectrum stronger and somewhat blue-shifted in nonpolar aromatic solvents as compared with solvents like heptane, hexane, and carbon tetrachloride.

Joel

I very much appreciate an answer from an expert like you are. I was not aware of the

interaction of iodine and aromatics.

And yes indeed its the publication by Benesi & Hildebrand.

Actually my reaction was towards mr Barbooti mentioning he had a gas-phase spectrum of iodine measured in 1985; just to show that iodine is a classical example for UV-Vis spectroscopy. I myself measured the spectrum in undergraduate practical class in the end of the sixtied with a classical glass plate spectrograph

Harry

Thanks, actually we used the spectral absorption of iodine in 1985 to improve the efficiency of a solar collector and not studied the spectrum itself/ The iodine vapor caused a rtemarkable increase in the process. Regards

Mahmood

Mahmood

Aand thank you for this information on a totally new aspect for me of the use of iodine absorption

The iodine absorption in inert non polar and polar solvents is interesting also from the theoretical point of view. From Raman studies in polar solvents, such as alcohols and ethers( see articles by L.D'Hoodge et als, Optics Comm.9,201-205(1973) and A.Laforgue and T.Theophanides, J.Mol. Structure.,6,203(1982)). In inert gasses like Ar are formed Hessel complexes, ArI2 and Ar2I2 type, whereas, in polar complexes we have Lewis Acid- Base complexes, I2... Alcohol , I2..... Ether complexes