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Fumaric acid has pK a values of approximately 3.0 and 4.5. By contrast, maleic acid has p K a values of approximately 1.5 and 6.5. The reason for this large difference is that when one proton is removed from the cis isomer (maleic acid) a strong intramolecular hydrogen bond is formed with the nearby remaining carboxyl group.
Fumaric acid or trans-butenedioic acid is an organic compound with the formula HO 2 CCH=CHCO 2 H. A white solid, fumaric acid occurs widely in nature. It has a fruit-like taste and has been used as a food additive. Its E number is E297. [3] The salts and esters are known as fumarates. Fumarate can also refer to the C 4 H 2 O 2− 4 ion (in ...
Cotinine has an in vivo half-life of approximately 20 hours, and is typically detectable for several days (up to one week) after the use of tobacco. The level of cotinine in the blood, saliva, and urine is proportionate to the amount of exposure to tobacco smoke, so it is a valuable indicator of tobacco smoke exposure, including secondary (passive) smoke. [14]
Maleic acid has a heat of combustion of -1,355 kJ/mol., [6] 22.7 kJ/mol higher than that of fumaric acid. Maleic acid is more soluble in water than fumaric acid. The melting point of maleic acid (135 °C) is also much lower than that of fumaric acid (287 °C). As confirmed by X-ray crystallography, maleic acid is planar.
Fumaric acid (E)-Butenedioic acid: trans: ... These compounds are weak dibasic acids with pK a tending towards values of ca. 4.5 and 5.5 as the separation between the ...
The first medical use of fumaric acid was described in 1959 by Walter Schweckendiek, a German chemist, [15] and was a topical formulation for psoriasis. The Swiss company Fumapharm eventually brought Fumaderm, an oral formulation of dimethyl fumarate (along with some monoesters) to market for psoriasis in Germany in 1994.
The systematic IUPAC name is not always the preferred IUPAC name, for example, lactic acid is a common, and also the preferred, name for what systematic rules call 2-hydroxypropanoic acid. This list is ordered by the number of carbon atoms in a carboxylic acid.
When the difference between successive pK a values is less than about 3, there is overlap between the pH range of existence of the species in equilibrium. The smaller the difference, the more the overlap. In the case of citric acid, the overlap is extensive and solutions of citric acid are buffered over the whole range of pH 2.5 to 7.5.