Amyl nitrite

Amyl nitrite is the chemical compound with the formula C₅H₁₁ONO. A variety of isomers are known, but they all feature an amyl group attached to the nitrito functional group. The alkyl group is unreactive and the chemical and biological properties are mainly due to the nitrite group. Like other alkyl nitrites, amyl nitrite is bioactive in mammals, being a vasodilator, which is the basis of its use as a prescription medicine. As an inhalant, it also has a psychoactive effect, which has led to its recreational use.

Nomenclature

The term "amyl nitrite" encompasses several isomers. For example, a common form of amyl nitrite with the formula (CH₃)₂CHCH₂CH₂ONO may be more specifically referred to as isoamyl nitrite. When the amyl group is a linear or normal (n) alkyl group, the resulting amyl nitrite would have the structural formula CH₃(CH₂)₄ONO.

Despite a very similar name to amyl nitrite, amyl nitrate has a different chemical composition and different properties.

Synthesis and reactions

Alkyl nitrites are prepared by the reaction of alcohols with nitrous acid:^[1]

C₅H₁₁OH + HONO → C₅H₁₁ONO + H₂O

The reaction is called esterification. Synthesis of alkyl nitrites is, in general, straightforward and can be accomplished in home laboratories. A common procedure includes the dropwise addition of concentrated sulfuric acid to a cooled mixture of an aqueous sodium nitrite solution and an alcohol. The intermediately-formed stoichiometric mixture of nitrous and nitric oxide then converts the alcohol to the alkyl nitrite, which, due to its low density, will form an upper layer that can be easily decanted from the reaction mixture.

Isoamyl nitrite decomposes in the presence of base to give nitrite salts and the isoamyl alcohol:

C₅H₁₁ONO + NaOH → C₅H₁₁OH + NaNO₂

Amyl nitrite, like other alkyl nitrites, reacts with carbanions to give oximes.^[2]

Amyl nitrites are also useful as reagents in a modification of the Sandmeyer reaction. The reaction of the alkyl nitrite with an aromatic amine in a halogenated solvent produces a radical aromatic species, this then abstracts a halogen atom from the solvent. For the synthesis of aryl iodides diiodomethane is used,^[3][4] whereas bromoform is the solvent of choice for the synthesis of aryl bromides.^[5]

Physiological effects

Amyl nitrite, in common with other alkyl nitrites,^[6] is a potent vasodilator (i.e., it expands blood vessels, resulting in lowering of the blood pressure). Alkyl nitrites function as a source of nitric oxide, which signals for relaxation of the involuntary muscles. Physical effects include decrease in blood pressure, headache, flushing of the face, increased heart rate, dizziness, and relaxation of involuntary muscles, especially the blood vessel walls and the anal sphincter. There are no withdrawal symptoms. Overdose symptoms include nausea, emesis (vomiting), hypotension, hypoventilation, dyspnea (shortness of breath), and syncope (fainting). The effects set in very quickly, typically within a few seconds and disappear soon after (within minutes).

It induces the formation of methemoglobin, which sequesters cyanide as nontoxic cyanomethemoglobin.^[7]

Applications

Amyl nitrite is employed medically to treat heart diseases such as angina and also to treat cyanide poisoning.^[8] It is also used as an inhalant drug that induces a brief euphoric state, and when combined with other intoxicatant stimulant drugs such as cocaine or ecstasy (see MDMA), the euphoric state intensifies and is prolonged. Once some stimulative drugs wear off, a common side effect is a period of depression or anxiety, colloquially called a "come down"; amyl nitrite is sometimes used to combat these negative after-effects. This effect, combined with its dissociative effects, makes it an attractive but risky recreational drug (see poppers).^[9]

References

External links

• Kjonaas, Richard A. (1996). "Amyl: A Misunderstood Word". Journal of Chemical Education 73 (12): 1127. doi:10.1021/ed073p1127.  Editorial on the use of the word "amyl".