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farrid@lib107.its.rpi.edu (Dinah Thiers Farrington) wrote:
>
>searching for a TLC solvent system, and gotten unusual results. I am
>using silica plates, and I<2 to develop them. Instead of dark spots, I
>see a large white spot  with a rim of darker staining. Absolutely
>nothing in the white spot is picking up the iodine, and I'm quite sure
>this is not something contaminating the silica before the plate is
>developed. Has anyone seen this behavior?  Any explanation  of this, or
>anyreferences describing this would be greatly appreciated. This
>happened so far with solvents of 1:99 ratio of methanol to CH<2Cl<2  and
>5:95 CH<2Cl<2 to ether.( Whatis the explanation for I<2 marking the compounds,
>anyway?)
>      
>     2. I'm trying to visualize Br-CH<2CH<2CH<2-SH and
>SH-CH<2CH<2CH<2-OH BY this method. Anyone who has separated short chain 
>thiols  could help me greatly by sending me a note about what systems
>they found successful.
>                                        Thank You,
>                                        Dinah Farrington


Iodine oxidizes thiols to disulfides, and probably other stuff.  
Iodide is colorless.  You might try spraying with phosphomolybdic acid in 
MeOH, and heating.  The pale background will be deep blue where it reacts 
with reducing substances.

There are things worse than thiols.  Ever smell p-chlorophenylisocyanide? 
 It overpowers ethyl mercaptan.

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