The chemistry of N,N′-dimethylformamidine. I. Formation from potassium methylamide and its thermal stability

Abstract

Can. J. Chem. 56, 1455.The thernial decomposition of methylamine solutions of potassium methylaniide (PMA) t o form the potassium salt (PDMFA) of N,N'-dimethylformaniidine (DMFA) has been studied as a function of PMA concentration at 60°C. Although concentrated solutions yield normal pseudo-first-order plots (analysis by ultraviolet-visible spectrophotornetry), dilute solutions (<0.05 mol L-' PMA) show an increase to a new rate after about 20 h reaction.The mechanism for this novel amidine salt synthesis is discussed in terms of rate-limiting e-hydride elimination from the PMA ion pair. The relatively sharp rate increase with time for the low concentration runs may arise from a slow buildup of one or more intermediates. The resulting inverse dependence of k,,, on PMA concentration is probably related to ion pairdimer association phenomena.Pure DMFA has been produced by this reaction, and its thernial stability examined. DMFA decomposes above 100'C to form bis-N-(N'-methylmethylenin~ine)methylamine and niethylamine; the series of equilibria involved have been shown to be reversible.On a etudie, en fonction de la concentration de la MAP a GOT, la deconlposition thermique On a pu produire de la DMFA pure par cette rtaction et on a tvalue sa stabilitk thermique. La DMFA se decompose au-dessus de 100°C pour conduire a de la bis-N-(N'-methylmethylcnimine) methylamine et a de la methylamine; on a montre que la strie des iquilibres impliques est reversible.[Traduit par le journal]Although there are few references in the literThe potassium salt of DMFA had been identified2 ature to N,Nf-dimethylformamidine (DMFA) (I), as one of the major products formed when a solution ~ -the general chemistry of the amidine group,

The chemistry of N,N′-dimethylformamidine. II. Hydrolysis. Kinetically controlled formation of cis-N-methylformamide

“…The synthesis, identification, and purification of D M F A of Canada Ltd., CRNL, 1969CRNL, -1972 have been reported elsewhere in this series (1 For personal use only.…”

The dissociation constant for potassium methylamide ion pairs in methylamine

“…A 1 m long vacuum-jacketed column, based on a design in the literature (18), was operated under reflux with cooling fluid pumped through the central condenser tube at about -21°C (bp NH, -33.4"C, CH,NH, -65°C). By removing up to eight 2 ml condensed vapour samples from the top of the column over a period of 48 h, it was possible to decrease the NH, content o f the methylthe salts (5 For personal use only. In spite of this ability to obtain methylamine initially very low in NH,, it was found impossible to maintain a low level for any useful period of time.…”

“…In eq. [5], e is the electronic charge and Ic the Boltzmann constant. N o allowance is made for specific ions o r solute-solvent interactions.…”

“…T h e agreement between theoretical and experimental K , is best for a value of "a" (in eq. [5]) just greater than 3 A. Delmas (20) chose 3 A for KNH, in ammonia, based o n the sum of the ionic radii for this salt.…”