The basicities of aliphatic amides

Abstract

We report pK, values in aqueous solution at 298 K of the protonated forms of several aliphatic amides, viz., acetamide (pK, = -0.62 + 0.07), N-methylacetamide (-0.42 + 0.03), N,N-dimethylacetamide (-0.28 + 0.03), N,N-dimethylformamide (-1 . 2 + 0.5), urea (0.053 + 0.002) and thiourea (-0.9rf:O.l). pK, values are also reported for protonated acetamide and urea in aqueous solution in the temperature range 5-40°C and in D,O. A previously described conductimetric method was used for all measurements.

Determination of protonation constants and structural correlations for some tertiary formamides and acetamides in sulfuric acid with UV spectroscopy

“…On the other hand, our value obtained by BOM is close to the value of -0.62, which was determined by the conductometric method [23]. Values for DMA (-0.29) do not comply with some literature data (-0.21) [16,20], but are practically equal to the value of -0.28 obtained by Grant et al [23].…”

“…The pK BH + value of -1.13 for DMFA coincides with that given by Bagno and Scorrano [20], and is close to the value of -1.2 from Grant and coworkers [23]. However, the pK BH + value for DMFA differs from the value of -1.33, which is published by Liler [17].…”

“…Additionally, it is subjected to further hypsochromic shift caused by protonation [16]. One of the few methods which is used to determine the basicities of some aliphatic amides is the conductimetric method used by Grant and coauthors [23]. Basicity and solvation of aliphatic amides are intrinsically important parameters for understanding the behavior of biochemical systems.…”

Heterocycles with 7 and 8π electrons. Models for flavin and pteridine intermediates and candidates for novel inorganic rings

“…(3)), as has been suggested for the corresponding reaction of methylviologen dications in strongly alkaline solution [198]. The smaller pyrazine system with two positive charges concentrated within one six-membered ring is obviously much more acidic and does not even tolerate relatively weakly basic solvents such as DMF (pKBH+ = --1.2 [199]), water (--1.74), or alcohols (~ -2), but only extremely weak bases such as acetonitrile (pKBH+ = 10.1 [200]). …”

NACE for the analysis of acrylamide in food

“…The theoretical pH value of this electrolyte was reported as ,2.1 [20]. Literature values of pK aHB1 for DMF in water lies between 21.2 and 21.13 [24,25] and for benzamide between 22.16 and 21.54 [26,27]. The pK aHB1 values of these analytes in ACN increase to 16.1 and 13.76, respectively [21].…”