I would try to evolve HCl gas from a dry chloride salt (preferably alkaline metal chlorides) by dropping conc. H2SO4 onto it and driving the gas into previously dried DMF. However, if you have access to pressurized HCl gas tanks, I would choose them over the acid-base approach.
Dry DMF may be obtained with barium oxide and 4A molecular sieves (see link).
http://chem.libretexts.org/Core/Analytical_Chemistry/Lab_Techniques/Distillation/Drying_Solvents
I would try to evolve HCl gas from a dry chloride salt (preferably alkaline metal chlorides) by dropping conc. H2SO4 onto it and driving the gas into previously dried DMF. However, if you have access to pressurized HCl gas tanks, I would choose them over the acid-base approach.
Dry DMF may be obtained with barium oxide and 4A molecular sieves (see link).
http://chem.libretexts.org/Core/Analytical_Chemistry/Lab_Techniques/Distillation/Drying_Solvents
Another approach might be to first synthesize the Vilsmeier-Haack-reagent, dissolve it in an appropriate volume of DMF and hydrolyze the reagent with a slight excess of water. The slight remainders of water may then be sequestered by the above mention molecular sieve.
EDIT: Using molecular sieve in this approach is a bad idea since it also sequesters HCl (http://www.sigmaaldrich.com/chemistry/chemical-synthesis/learning-center/technical-bulletins/al-1430/molecular-sieves.html)
Dear Ekaterina,
DMF (N,N-dimethylformamide): Decomposes slowly at room temperature and more rapidly at reflux, releasing dimethylamine and carbon monoxide. This decomposition is catalysed by acidic and basic impurities, and standing DMF for several hours at room temperature with basic drying agents such as calcium hydride or sodium hydroxide leads to noticeable decomposition. Dry DMF can be prepared by drying overnight over barium oxide or 4A molecular sieves, followed by decantation of the drying agent and vacuum distillation (~20 mmHg is a sufficient vacuum to lower the boiling point over DMF to a reasonable value). Dry DMF can be stored over 4A molecular sieves.
Generally, HCl can contained in tank is dry.
Therefore, to obtain dry DMF saturated with HCl, you pass HCl from the tank to the previously dried DMF until saturation.
For more on how to dry organic solvents, please see the publication contained in the following link:
http://chem.libretexts.org/Core/Analytical_Chemistry/Lab_Techniques/Distillation/Drying_Solvents
Hoping this will be helpful,
Rafik
- Badges
- Science topic