Base (chemistry)
From Wikipedia, the free encyclopedia
 | This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2010) |
Bases can be thought of as the chemical opposite of acids. A reaction between an acid and base is called neutralization. Bases and acids are seen as opposites because the effect of an acid is to increase the hydronium ion (H3O+) concentration in water, whereas bases reduce this concentration. Bases react with acids to produce water and salts (or their solutions).
Contents[show] |
[edit] Definitions
Main article: acid-base reaction theories
A strong base is a base which hydrolyzes completely, raising the pH of the solution toward 14. Concentrated bases, like Concentrated acids, attack living tissue and cause serious burns. They react differently to skin than acids do, so while strong acids are corrosive, strong bases are referred to as caustic. Superbases are a class of especially basic compounds and non-nucleophilic bases are a special class of strong bases with poor nucleophilicity. Bases may also be weak bases such as ammonia, which is used for cleaning. Arrhenius bases are water-soluble and these solutions always have a pH greater than 7. An alkali is a special example of a base, where in an aqueous environment, hydroxide ions are donated. There are other more generalized and advanced definitions of acids and bases.The notion of a base as a concept in chemistry was first introduced by the French chemist Guillaume François Rouelle in 1754. He noted that acids, which in those days were mostly volatile liquids (like acetic acid), turned into solid salts only when combined with specific substances. Rouelle considered that such a substance serves as a base for the salt, giving the salt a "concrete or solid form”.[3]
Forms of cocaine
Salts
Cocaine, like many alkaloids can form many different salts, such as hydrochloride (HCl) and sulfate (-SO4). Different salts have different solvency in solvents. Its hydrochloride, like many alkaloid hydrochloride is polar and is soluble in water.Basic
Main article: Freebase (chemistry)
As the name implies, “freebase” is the base form of cocaine, as opposed to the salt form. It is practically insoluble in water whereas hydrochloride salt is water soluble.Smoking freebase cocaine has the additional effect of releasing methylecgonidine into the user's system due to the pyrolysis of the substance (a side effect which insufflating or injecting powder cocaine does not create). Some research suggests that smoking freebase cocaine can be even more cardiotoxic than other routes of administration[38] because of methylecgonidine's effects on lung tissue[39] and liver tissue.[40]
Pure cocaine is prepared by neutralizing its compounding salt with an alkaline solution which will precipitate to non-polar basic cocaine. It is further refined through aqueous-solvent Liquid-liquid extraction.
Forms of cocaine
Salts
Cocaine, like many alkaloids can form many different salts, such as hydrochloride (HCl) and sulfate (-SO4). Different salts have different solvency in solvents. Its hydrochloride, like many alkaloid hydrochloride is polar and is soluble in water.Basic
Main article: Freebase (chemistry)
As the name implies, “freebase” is the base form of cocaine, as opposed to the salt form. It is practically insoluble in water whereas hydrochloride salt is water soluble.
Smoking freebase cocaine has the additional effect of releasing methylecgonidine into the user's system due to the pyrolysis of the substance (a side effect which insufflating or injecting powder cocaine does not create). Some research suggests that smoking freebase cocaine can be even more cardiotoxic than other routes of administration[38] because of methylecgonidine's effects on lung tissue[39] and liver tissue.[40]Pure cocaine is prepared by neutralizing its compounding salt with an alkaline solution which will precipitate to non-polar basic cocaine. It is further refined through aqueous-solvent Liquid-liquid extraction.
Crack cocaine
Crack is a lower purity form of free-base cocaine and contains sodium bicarbonate as impurity. Freebase and crack are often administered by smoking.[41] The origin of the name is from the crackling sound (hence the onomatopoeic “crack”) produced when cocaine containing impurities are heated.[42]
