Caffeine chemical properties

Caffeine and theophylline have pharmaceutically important chemical properties. Both arc weak BrOnsted bases. The reported pK values are 0.8 and 0.6 fur caffeine and 0.7 for theophylline. These values represent the basicity of the imino nitrogen at position 9. As acids, caffeine has a pK., above 14. and theophylline, a pK., of 8.8. In theophylline, a proton can be donated from position 7 (i.e.. it can act as a Bronsted acid). Caffeine cannoi donate a proton from position 7 and does not act as a Bretnsted acid at pH values under 14. Caffeine docs have electrophilic sites at positions I. 3. and 7. In addition to its Bronsted acid site at 7. theophylline has electrophilic sites at I and 3. In condensed terms, both compounds arc electron-pair donors, but only theophylline is a proton donor in most pharmaceutical system.s. 

One of the approaches found most suitable to explain the sensorial properties of sweet, bitter, and sweet-bitter substances proves to be the physico-chemical approach especially as concerns hydration and surface properties (DeSimone and Fleck, 1980 Funasaki et al., 1996 Fimasaki et al., 1999 Mathlouthi and Hutteau, 1999). Thus, solution properties of sweet and bitter molecules were found informative on their type of hydration (hydrophobic or hydrophilic) and on the extent of the hydration layer (Fiutteau et al., 2003). Physico-chemical properties (intrinsic viscosity, apparent specific volume, and surface tension) and NMR relaxation rates of the aqueous solutions of sucrose, caffeine, and sucrose-caffeine mixtures were used in the interpretation of the taste modalities of these molecules and to explain the inhibition of caffeine bitterness by sucrose (Aroulmoji et al., 2001). Caffeine molecules were found to form an adsorption layer whereas sucrose induces a desorption layer at the air/water interface. The adsorption of caffeine gradually increases with concentration and is delayed when sucrose is added in the caffeine solution (Aroulmoji et al., 2004). 

Caffeine was first studied scientifically by two French chemists, Joseph Bienaime Caventou (1795-1877) and Pierre Joseph Pelletier (1788-1842), who were very interested in the chemical properties of the alkaloids. Between 1817... 

Psychotropic compounds, such as caffeine and nicotine, can exist in air as a result of their release in tobacco smoke or when certain drugs or essences are inhaled as vapors. These psychotropic substances belong to various classes of organic compounds with different physico chemical properties and different routes of release into the environment, so they may exist in the gaseous or asparticulates and as native compounds or derivatives. For instance, nicotine is mostly gaseous when it is a free base, but combines with tobacco smoke particles when in acidic form (Liang and Pankow, 1996). Cocaine and heroin in the atmosphere presumably exist mainly as solid particulates (Dindal et al., 2000 Cecinato and Balducci, 2007). 

How would you describe the differences between a cup of coffee and a cup of hot water What probably come to mind are the aroma, the dark color, and the taste of a good cup of coffee. Coffee s action as a stimulant is another obvious difference. These properties come from the chemical compounds that hot water dissolves from ground coffee beans. These compounds are molecules constructed from different atoms bound together in veiy specific arrangements. The molecule that makes coffee a stimulant is caffeine. Our background photo is a magnification of crystals of pure caffeine, and the inset is a ball-and-stick model of this molecule. 

Many pharmacologically active organic chemicals fonnd in natnre are alkaloids. In general, these componnds contain one or more nitrogen atoms, which in turn impart some basicity to the molecnle. Well-known alkaloid examples are caffeine, cocaine, codeine, ephedrine, morphine, nicotine, qninine, and scopolamine. Heroin is derived from morphine by a chemical modification that increases lipophilicity, making the heroin molecnle inherently more pharmacologically potent than morphine. The exhibition of its basic properties by an alkaloid (Aik) involves (by definition) the acceptance of a proton H+ according to ... 

Chocolate has antioxidant properties for low-density lipoproteins and hence could prevent heart disease. Foods and beverages derived from cocoa beans have been consumed by humans since 460 a.d. Cocoa pods from the cocoa tree (Theobroma cacao) are harvested and the beans removed and fermented. Dried and roasted beans contain about 300 chemicals including caffeine, theobromine, and phenethylamine. Chocolate liquor is prepared by finely grinding the nib of the cocoa bean and is the basis for all chocolate products. Cocoa powder is made by removing part of the cocoabutter from the liquor. Bittersweet chocolate, sometimes called dark chocolate, contains between 15 and 60% chocolate liquor, the remainder being cocoa butter, sugar, and other additives. Milk chocolate is the predominant form of chocolate consumed in the U.S. and typically contains 10 to 12% chocolate liquor. 

Organic synthesis is the construction of complex organic compounds from simple starting compounds by a series of chemical reactions. The compounds synthesized in nature are called natural products. Nature provides a plethora of organic compounds and many of these possess interesting chemical and pharmaceutical properties. Examples of natural products include cholesterol (1.1), a steroid found in most body tissues limonene (1.2), a terpene found in lemon and orange oils caffeine (1.3), a purine found in tea leaves and coffee beans and morphine (1.4), an alkaloid found in opium. 

Many of the chemicals used in this course will be unfamiliar to you. Their properties can be looked up in reference books, a very useful one being the Aldrich Catalog Handbook of Fine Chemicals. It is interesting to note that 1,4-dichlorobenzene is listed as a toxic irritant and naphthalene is listed as an irritant. Both are used as moth balls. Camphor, used in vaporizers, is classified as a flammable solid irritant. Salicylic acid, which we will use to synthesize aspirin (Chapter 26) is listed as moisture-sensitive toxic. Aspirin (acetylsalicyclic acid) is classified as an irritant. Caffeine, which we will isolate from tea or cola syrup (Chapter 8), is classified as toxic. Substances not so familiar to you—1-naphthol and benzoic acid—are classified respectively as toxic irritants and irritant. To put things in some perspective, nicotine is classified as highly toxic. ... 

Tan et al. [4] proposed to use a thin silica membrane (prepared by them), which presents hydrophilic properties. They obtained very interesting results, i.e., arejection rate and a permeability of 0.98 and 4.4 x 10 mol s Pa , respectively (see Table 7.1). To underline the effects of adsorption, the same membrane was turned hydrophobic by chemical vapor deposition (CVD) treatment and tested. A very low rejection was obtained and no significant selectivity was given by this membrane. On the basis of the fact that caffeine has more affinity with hydrophilic surfaces, these results gave evidence that adsorption was the major mechanism. Therefore, adsorption phenomenon should be taken into account for membrane choice to control solute/membrane interactions. 

Bungert K. and Eichner K. (2000) Radical scavenging and antioxidative properties of phenolic compounds in relation to their chemical structure Am. Chem. Soc. Symp. Ser. (Caffeinated Beverages) Chem. Abstr. 13, 88522)754, 119 134. 

New complex compounds of general formula Zn(4-ClC6H3-2-(0H)C00 2 L2 nH20 (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2,3), were prepared and characterized by Gyoryova and coworkers [230], vfho studied their thermal properties by TG/DTG and DTA methods. Thermal decomposition of the hydrated compounds starts with the release of water molecules. During the thermal decomposition of the anhydrous compounds, the release of organic ligands take place, followed by the decomposition of the salicylate anion. Zinc oxide was the final solid product of the thermal decomposition performed up to 650 C. TG, powder XRD, IR spectra and chemical analysis were used for the determination of the products of the thermal decomposition. 

Most alkaloids have basic properties coimected with a heterocyclic tertiary nitrogen. Notable exceptions are colchicine, caffeine, and paclitaxel. Most alkaloids are biosynthetically derived from amino acids such as phenylalanine, tyrosine, tryptophan, ornithine, and lysine. Alkaloids represent a wide variety of chemical structures. About 20000 alkaloids are known, most being isolated from plants. But alkaloids have also been found in microorganisms, marine organisms such as algae, dinoflagellates, and puffer fish, and terrestrial animals such as insects, salamanders, and toads. 

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