An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are relatively stronger acids. Alcohols, with –OH, can act as acids but they are usually very weak. The relative stability of the conjugate base of the acid determines its acidity. Other groups can also confer acidity, usually weakly: the thiol group –SH, the enol group, and the phenol group. In biological systems, organic compounds containing these groups are generally referred to as organic acids.
Organic acids are characterized by the presence of positively polarized hydrogen atom. There are two kinds of organic acids, the first of a hydrogen atom bonded to oxygen atoms, such as methyl alcohol and acetic acid. Second, the hydrogen atoms attached to the carbon atoms in which the carbon atoms are bonded directly to the carbonyl group (C = O), such as acetone. In general, organic acids are weak acids and do not dissociate completely in water, whereas the strong mineral acids do. Lower molecular mass organic acids such as formic and lactic acids are miscible in water, but higher molecular mass organic acids, such as benzoic acid, are insoluble in molecular (neutral) form.On the other hand, most organic acids are very soluble in organic solvents. p-Toluenesulfonic acid is a comparatively strong acid used in organic chemistry often because it is able to dissolve in the organic reaction solvent.Exceptions to these solubility characteristics exist in the presence of other substituents that affect the polarity of the compound.
Simple organic acids like formic or acetic acids are used for oil and gas well stimulation treatments. These organic acids are much less reactive with metals than are strong mineral acids like hydrochloric acid (HCl) or mixtures of HCl and hydrofluoric acid (HF). For this reason, organic acids are used at high temperatures or when long contact times between acid and pipe are needed.The conjugate bases of organic acids such as citrate and lactate are often used in biologically-compatible buffer solutions.Citric and oxalic acids are used as rust removal. As acids, they can dissolve the iron oxides, but without damaging the base metal as do stronger mineral acids. In the dissociated form, they may be able to chelate the metal ions, helping to speed removal.Biological systems create many and more complex organic acids such as L-lactic, citric, and D-glucuronic acids that contain hydroxyl or carboxyl groups. Human blood and urine contain these plus organic acid degradation products of amino acids, neurotransmitters, and intestinal bacterial action on food components. Examples of these categories are alpha-ketoisocaproic, vanilmandelic, and D-lactic acids, derived from catabolism of L-leucine and epinephrine (adrenaline) by human tissues and catabolism of dietary carbohydrate by intestinal bacteria, respectively.
Organic base is characterized by the presence of atoms with a lone pair of electrons that can bind protons. Yangmengandung compounds of nitrogen atom is an example of an organic base, but the oxygen-containing compounds can also bertindaksebagai base when reacted with a strong acid. It should be noted that compounds containing oxygen atoms can act as an acid or alkaline, depending on the environment.
An organic base is an organic compound which acts as a base. Organic bases are usually, but not always, proton acceptors. They usually contain nitrogen atoms, which can easily be protonated. Amines and nitrogen-containing heterocyclic compounds are organic bases. Examples include:
* methyl amine
* phosphazene bases
* Hydroxides of some organic cations
Factors affecting alkalinity
While all organic bases are considered to be weak, many factors can affect the alkalinity of the compounds. One such factor is the inductive effect. A simple explanation of the term would state that electropositive atoms (such as carbon groups) attached in close proximity to the potential proton acceptor have an “electron-releasing” effect, such that the positive charge acquired by the proton acceptor is distributed over other adjacent atoms in the chain. The converse is also possible as alleviation of alkalinity: electronegative atoms or species (such as fluorine or the nitro group) will have an “electron-withdrawal” effect and thereby reduce the basicity. To this end, trimethylamine is a more potent base than merely ammonia, due to the inductive effect of the methyl groups allowing the nitrogen atom to more readily accept a proton and become a cation being much greater than that of the hydrogen atoms. In guanidines, the protonated form (guanidinium) has three resonance structures, giving it increased stability and making guanadines stronger bases.
Phosphazene bases also contain phosphorus and are, in general, more alkaline than standard amines and nitrogen-based heterocyclics. Protonation takes place at the nitrogen atom, not the phosphorus atom to which the nitrogen is double-bonded.