[kriggy]

Hi guys,
by doing synthesis of 2-chlormethylpyridine we got this weird peaks at 5,07 and 4,84  ppm. I have little experience with NMR spectra but I was told that it is not substitution on pyridine ring because that would remove one of the peaks in 7-9 ppm area and because the peak moved from 5,07 to 4,84 ppm we suppose that it did react with SOCl₂ in the last step. The procedure I used is here:

a) Picolinic acid was dissolved in Me-OH and  after adding few droplets of concentrated H₂SO₄ was refluxed overnignt. After evaporation of solvent and adjusting pH to ~9 was extracted by CHCl₃ (3x) and Ethylacetate (1x) to get methylester as a yellow oil.

b) Ester was dissolved in THF and NaBH4 was added and the mixture was stirred overnight. After evaporation of solvent conc. HCl was added until pH was ~3 and then the acid was neutralized by solution of NaHCO3 until strongly basic pH. The solution was extracted by ethylacetate. Because the reduction was complete only from ~40% (shown by NMR I dont have home...) it was done again:
Dissolved in THF and borohydride was added. The mixture was refluxed while MeOH was added dropwise. After one hour the solution of NH₄Cl was added and after one more hour of stirring the solution was extracted by ehtylacetate.

c) Hydroxymethylpyridine was dissolved in CHCl₃ and cooled to 0°C. SOCl₂ was added dropwise in that rate that temperature didnt rise above 10°C (it did however rise to about 35°C once because wasnt careful and added too much SOCl₂) after adding all SOCl₂ mixture was stirred for 45 minutes and then Na₂CO₃ was added. Mixture was extracted by CHCl₃, the oganic phase was washed by water and dried over Na₂SO₄ and evaporated.
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hydroxymethylpyridine NMR (product of reaction b)

chlormethylpyridine NMR (product of reaction c)
From looking at my NMR chart i can see some possibilities but they just dont match together and they seem to be realy unlikely. Can NaBH₄ convert ester to ether? (doubt it) Or can it create something like this? (missing 3 hydrogens on carbon and oxygens but I cant figure it out how to put them there).
Thank you for any help.

[Babcock_Hall]

This is little better than a WAG, but suppose 2-chloromethylpyridine (or an intermediate in the chlorination) reacted with another molecule of 2-chloromethylpyridine, to form a salt in which there was a pyridinium nitrogen next to a -CH₂- group.  From the literature of alkylation of pyridine derivatives and from my own experience, the methylene group shows up around 4.65 to 4.9 ppm.  I don't think that this is a likely explanation, because I would anticiplate that the hydrogen atom at position-6 of the pyridine ring would also move downfield (roughly to 9 ppm, or so).  Also, the alkylations with which I am most familiar were done at elevated temperatures. 

[Archer]

Have you got your GCMS data?

[kriggy]

@Babcock_Hall: I realize that it is not much data.. I see one problem with your explanation and that is that the impurity was present also in the hydroxymethylpyridine. What exactly do you mean by elevated temperature? 100°C?

@Archer: I dont have it yet. Im not at school and my teacher has vacation but we are going to do it but will take some time. It is almost impossible to figure the impurity out with only NMR right? 

[Archer]

If you will take advice from an experienced spectroscopist of unknown substances, I would wait until you have a full set of data before you try to solve a puzzle. You are just speculating on the data obtained from one technique, you could spend weeks on this and then find you were barking up completely the wrong tree when you see the MS and/or IR data.

[Babcock_Hall]

We have done these alkylations in refluxing acetonitrile.  Your point that the impurity is in the hydroxymethylpyridine is well taken.