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It is weakly basic (pK a of conjugate acid = ~0.6) requiring strong acid to protonate it. [198] Caffeine does not contain any stereogenic centers [199] and hence is classified as an achiral molecule. [200] The xanthine core of caffeine contains two fused rings, a pyrimidinedione and imidazole.
Caffeine Properties Chemical formula. C 8 H 10 N 4 O 2: Molar mass: 194.194 g·mol −1 Appearance Odorless, white needles or powder Density: 1.23 g/cm 3, solid [1]
A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is used. The simplest anion which can be a conjugate base is the free electron in a solution whose conjugate acid is the atomic hydrogen.
In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), usually denoted by H +, to an atom, molecule, or ion, forming a conjugate acid. [1] (The complementary process, when a proton is removed from a Brønsted–Lowry acid, is deprotonation.) Some examples include The protonation of water by ...
The chemical complexity of coffee is emerging, especially due to observed physiological effects which cannot be related only to the presence of caffeine. Moreover, coffee contains an exceptionally substantial amount of antioxidants such as chlorogenic acids, hydroxycinnamic acids, caffeine and Maillard reaction products, such as melanoidins. [3]
Free caffeic acid can be found in a variety of beverages, including brewed coffee at 63.1-96.0 mg per 100 ml [7] and red wine at 2 mg per 100 ml. [8] It is found at relatively high levels in herbs of the mint family, especially thyme, sage and spearmint (at about 20 mg per 100 g), and in spices, such as Ceylon cinnamon and star anise (at about 22 mg per 100 g).
Caffeine synthase is a methyltransferase enzyme involved in the caffeine biosynthesis pathway. It is expressed in tea species, coffee species, and cocoa species. The enzyme catalyses the following reactions: [ 1 ]
The conjugate acid [HP(MeNCH 2 CH 2) 3 N] + of the base has a pK a of 32.9 in acetonitrile. For comparison, the conjugate acid of triethylamine has a pK a near 17 in acetonitrile. Owing to its ability to deprotonate weak carbon acids, the Verkade base catalyzes a variety of condensation reactions .