PURPLE?!?!

Hmm, here’s a quick little puzzle that I’m in the middle of solving. If anyone knows the answer, feel free to let me know.

Attempting to make the acid chloride of 2-picolinic acid by SOCl2. In dichloromethane, combined ~5g of 2-picolinic acid with a slight excess of SOCl2 (~1.2:1), refluxed for ~20 minutes, removed solvent, set it aside. The initial solid was tan-brown. After a few days, it was dark. Massively dark. And green-blue, as far as the eye can tell. After a week, it’s bone dry and still massively dark. A rough yield of around 6g. So it picked up some mass…

Solubility testing… Very soluble in water, forms a deep purple solution. Soluble in methanol, solution is a bit more blue. Very slightly soluble in chloroform, purple solution. Very slightly soluble in acetonitrile, greenish leaning toward blue solution.

NMR (in D2O)… Four clean aromatic signals, consistent with the 4 protons of an ortho-substituted pyridine ring, nothing else.

20140204nmrpurple01

UV-Vis (in water)… Peak at ~540nm, shoulder at ~650nm. Strong peak at ~260nm.

20140204uvvis01 20140204uvvis02

This has not been exhaustively lit searched yet, but the intensity of the color of the product is intriguing AND a ~20% mass increase makes it a fun little puzzle. We will be exploring more…

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N-4-phenyl picolinamide {JBE0105}

N-4-phenyl picolinamide JBE0105

2012/09/08

Planning:

This is the 1-armed version of the ligands we’ve been trying to make. This synthesis is from {Organic Letters, 2011, 13, 9, 2256-2259, Kaname Sasaki and David Crich*} It looks like a pretty simple reaction between the carboxylic acid precursor (picolinic acid) and an isocyanate (phenylisocyanate) with an amine base.

Reactant Amount Moles Ratio
Picolinic acid 100mg C6H5O2N, 123.111g/mol 8.12mmol 1.5
Phenylisocyanate 0.59mL 1.096g/mL, C7H5NO, 119.12g/mol 5.42mmol 1
N,N-diisopropylethylamine 1.89mL 129.24g/mol, 0.742g/mL 10.84mmol 2
N,N-dimethylformamide (DMF) 40mL 10mL/mmol isocyanate

From the article, dissolve acid and amine in DMF, add isocyanate (single portion) and stir at 25°C for 2 hours. Remove volatiles under vacuum, purify by prep TLC (99:1 mix CHCl3:MeOH), white needles, Tm=72.6-74.0°C. Hopefully by scaling up it will crystallize without prep TLC.

Synthesis:

Reactant Amount Moles Ratio
Picolinic acid 110mg C6H5O2N, 123.111g/mol 0.894mmol 1
Phenylisocyanate 0.65mL 1.096g/mL, C7H5NO, 119.12g/mol 5.98mmol 6.7
N,N-diisopropylethylamine 2.0mL 129.24g/mol, 0.742g/mL 11.5mmol 13
DMF 25mL 10mL/mmol isocyanate

Combined picolinic acid and amine in DMF, stirred to dissolve at room temperature. Added phenylisocyanate as a single addition, slight orange color developed almost immediately. Addition at 8:25, 2012-09-08. Left to stir at RmTemp. RmTemp is always a bit less than 25degC and since the rxn is scaled up, it can react a bit longer. Color faded to pale yellow over a few hours.

2012-09-10 – ERROR – There was a decimal place mix up here. There should be MUCH more picolinic acid. Since the rxn is run at Rm Temp, I’ll try to salvage it by adding more and letting the rxn go a bit longer. Arg. Need 0.998g more picolinic acid.

Synthesis:

Reactant Amount Moles Ratio
Picolinic acid 0.110+1.000= 1.110g C6H5O2N, 123.111g/mol 9.02mmol 1.5
Phenylisocyanate 0.65mL 1.096g/mL, C7H5NO, 119.12g/mol 5.98mmol 1
N,N-diisopropylethylamine 2.0mL 129.24g/mol, 0.742g/mL 11.5mmol 1.9
DMF 25mL 10mL/mmol isocyanate

Additional picolinic acid added 14:30, 2012-09-10.

Open Notebooking/Live Blogging/#RealTimeChem

This is a new experiment for me. Inspired by a number of factors, my research students and I will be keeping open lab notebooks of the research we do at Minnesota State University Moorhead. This will allow everyone to see the great work we do here and will be a good way to keep ourselves up-to-date. The majority of the work posted here will be tentative and some of it may end up being just plain wrong, but that’s one of the exciting parts of science.