Nitrous oxide

Names
IUPAC names Nitrous oxide[1] (not recommended) Dinitrogen oxide[2] (alternative name)
Systematic IUPAC name Oxodiazen-2-ium-1-ide
Other names Laughing gas sweet air nitrous nos protoxide of nitrogen hyponitrous oxide dinitrogen oxide dinitrogen monoxide
Identifiers
CAS Number	10024-97-2 Y
3D model (JSmol)	Interactive image Interactive image
Beilstein Reference	8137358
ChEBI	CHEBI:17045 Y
ChEMBL	ChEMBL1234579 N
ChemSpider	923 Y
DrugBank	DB06690 N
ECHA InfoCard	100.030.017
E number	E942 (glazing agents, ...)
Gmelin Reference	2153410
KEGG	D00102 Y
PubChem CID	948
RTECS number	QX1350000
UNII	K50XQU1029 Y
UN number	1070 (compressed) 2201 (liquid)
CompTox Dashboard (EPA)	DTXSID8021066
InChI InChI=1S/N2O/c1-2-3 Y Key: GQPLMRYTRLFLPF-UHFFFAOYSA-N Y InChI=1/N2O/c1-2-3 InChI=1/N2O/c1-2-3 Key: GQPLMRYTRLFLPF-UHFFFAOYAP
SMILES N# ==O
Properties
Chemical formula	N 2O
Molar mass	44.013 g/mol
Appearance	colourless gas
Density	1.977 g/L (gas)
Melting point	−90.86 °C (−131.55 °F; 182.29 K)
Boiling point	−88.48 °C (−127.26 °F; 184.67 K)
Solubility in water	1.5 g/L (15 °C)
Solubility	soluble in alcohol, ether, sulfuric acid
log P	0.35
Vapor pressure	5150 kPa (20 °C)
Magnetic susceptibility (χ)	−18.9·10−6 cm3/mol
Refractive index (nD)	1.000516 (0 °C, 101.325 kPa)
Viscosity	14.90 μPa·s[3]
Structure
Molecular shape	linear, C∞v
Dipole moment	0.166 D
Thermochemistry
Std molar entropy (S⦵298)	219.96 J/(K·mol)
Std enthalpy of formation (ΔfH⦵298)	+82.05 kJ/mol
Pharmacology
ATC code	N01AX13 (WHO)
Routes of administration	Inhalation
Pharmacokinetics:
Metabolism	0.004%
Biological half-life	5 minutes
Excretion	Respiratory
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H270, H280, H281
Precautionary statements	P220, P244, P282, P317, P336, P370+P376, P403, P410+P403
NFPA 704 (fire diamond)	2 0 0 OX
Flash point	Nonflammable
Safety data sheet (SDS)	Ilo.org, ICSC 0067
Related compounds
Related nitrogen oxides	Nitric oxide Dinitrogen trioxide Nitrogen dioxide Dinitrogen tetroxide Dinitrogen pentoxide
Related compounds	Ammonium nitrate Azide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is YN ?) Infobox references

Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, nitro, or nos,^[4] is a chemical compound, an oxide of nitrogen with the formula N
₂O. At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste.^[5] At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.

Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects.^[6] Its colloquial name, "laughing gas", coined by Humphry Davy, is due to the euphoric effects upon inhaling it, a property that has led to its recreational use as a dissociative anaesthetic.^[6] It is on the World Health Organization's List of Essential Medicines.^[7] It is also used as an oxidiser in rocket propellants, and in motor racing to increase the power output of engines.

Nitrous oxide's atmospheric concentration reached 333 parts per billion (ppb) in 2020, increasing at a rate of about 1 ppb annually.^[8][9] It is a major scavenger of stratospheric ozone, with an impact comparable to that of CFCs.^[10] About 40% of human-caused emissions are from agriculture.^[11][12] Nitrogen is added to the soil via animal urine and dung, and synthetic fertilisers: micro-organisms then release it in nitrous oxide.^[13] Being the third most important greenhouse gas, nitrous oxide substantially contributes to global warming.^[14][15] Reduction of emissions is a popular topic in the politics of climate change.^[16]

Nitrous oxide is used as a propellant, and has a variety of applications from rocketry to making whipped cream. It is used as a recreational drug for its potential to induce a brief "high". Most recreational users are unaware of its neurotoxic effects when abused. When used chronically, nitrous oxide has the potential to cause neurological damage through inactivation of vitamin B12.

Uses

Rocket motors

Nitrous oxide may be used as an oxidiser in a rocket motor. It has advantages over other oxidisers in that it is much less toxic, and because of its stability at room temperature, it is also easier to store and relatively safe to carry on a flight. As a secondary benefit, it may be decomposed readily to form breathing air. Its high density and low storage pressure (when maintained at low temperatures) enable it to be highly competitive with stored high-pressure gas systems.^[17]

In a 1914 patent, American rocket pioneer Robert Goddard suggested nitrous oxide and gasoline as possible propellants for a liquid-fuelled rocket.^[18] Nitrous oxide has been the oxidiser of choice in several hybrid rocket designs (using solid fuel with a liquid or gaseous oxidiser). The combination of nitrous oxide with hydroxyl-terminated polybutadiene fuel has been used by SpaceShipOne and others. It also is notably used in amateur and high power rocketry with various plastics as the fuel.

Nitrous oxide also may be used in a monopropellant rocket. In the presence of a heated catalyst, N
₂O will decompose exothermically into nitrogen and oxygen, at a temperature of approximately 1,070 °F (577 °C).^[19] Because of the large heat release, the catalytic action rapidly becomes secondary, as thermal autodecomposition becomes dominant. In a vacuum thruster, this may provide a monopropellant specific impulse (I_sp) of as much as 180 s. While noticeably less than the I_sp available from hydrazine thrusters (monopropellant or bipropellant with dinitrogen tetroxide), the decreased toxicity makes nitrous oxide an option worth investigating.

Nitrous oxide is said to deflagrate at approximately 600 °C (1,112 °F) at a pressure of 309 psi (21 atmospheres).^[20] At 600 psi, for example, the required ignition energy is only 6 joules, whereas N
₂O at 130 psi a 2,500-joule ignition energy input is insufficient.^[21][22]

Internal combustion engine

In vehicle racing, nitrous oxide (often called "nitrous") allows the engine to burn more fuel by providing more oxygen during combustion. The increase in oxygen allows an increase in the injection of fuel, allowing the engine to produce more engine power. The gas is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures, about 570 degrees F (~300C). Therefore, it often is mixed with another fuel that is easier to deflagrate. Nitrous oxide is a strong oxidising agent, roughly equivalent to hydrogen peroxide, and much stronger than oxygen gas.

Nitrous oxide is stored as a compressed liquid; the evaporation and expansion of liquid nitrous oxide in the intake manifold causes a large drop in intake charge temperature, resulting in a denser charge, further allowing more air/fuel mixture to enter the cylinder. Sometimes nitrous oxide is injected into (or prior to) the intake manifold, whereas other systems directly inject, right before the cylinder (direct port injection) to increase power.

The technique was used during World War II by Luftwaffe aircraft with the GM-1 system to boost the power output of aircraft engines. Originally meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, technological considerations limited its use to extremely high altitudes. Accordingly, it was only used by specialised planes such as high-altitude reconnaissance aircraft, high-speed bombers and high-altitude interceptor aircraft. It sometimes could be found on Luftwaffe aircraft also fitted with another engine-boost system, MW 50, a form of water injection for aviation engines that used methanol for its boost capabilities.

One of the major problems of using nitrous oxide in a reciprocating engine is that it can produce enough power to damage or destroy the engine. Very large power increases are possible, and if the mechanical structure of the engine is not properly reinforced, the engine may be severely damaged or destroyed during this type of operation. It is important with nitrous oxide augmentation of petrol engines to maintain proper operating temperatures and fuel levels to prevent "pre-ignition",^[23] or "detonation" (sometimes referred to as "knock"). Most problems that are associated with nitrous oxide do not come from mechanical failure due to the power increases. Since nitrous oxide allows a much denser charge into the cylinder, it dramatically increases cylinder pressures. The increased pressure and temperature can cause problems such as melting the pistons or valves. It also may crack or warp the piston or cylinder head and cause pre-ignition due to uneven heating.

Automotive-grade liquid nitrous oxide differs slightly from medical-grade nitrous oxide. A small amount of sulfur dioxide (SO
₂) is added to prevent substance abuse.^[24]

Aerosol propellant

The gas is approved for use as a food additive (E number: E942), specifically as an aerosol spray propellant. Its most common uses in this context are in aerosol whipped cream canisters and cooking sprays.

The gas is extremely soluble in fatty compounds. In aerosol whipped cream, it is dissolved in the fatty cream until it leaves the can, when it becomes gaseous and thus creates foam. Used in this way, it produces whipped cream which is four times the volume of the liquid, whereas whipping air into cream only produces twice the volume. If air were used as a propellant, oxygen would accelerate rancidification of the butterfat, but nitrous oxide inhibits such degradation. Carbon dioxide cannot be used for whipped cream because it is acidic in water, which would curdle the cream and give it a seltzer-like "sparkling" sensation.

The whipped cream produced with nitrous oxide is unstable, and will return to a more liquid state within half an hour to one hour.^[25] Thus, the method is not suitable for decorating food that will not be served immediately.

In December 2016, some manufacturers reported a shortage of aerosol whipped creams in the United States due to an explosion at the Air Liquide nitrous oxide facility in Florida in late August. With a major facility offline, the disruption caused a shortage resulting in the company diverting the supply of nitrous oxide to medical customers rather than to food manufacturing. The shortage came during the Christmas and holiday season when canned whipped cream use is normally at its highest.^[26]

Similarly, cooking spray, which is made from various types of oils combined with lecithin (an emulsifier), may use nitrous oxide as a propellant. Other propellants used in cooking spray include food-grade alcohol and propane.

Medicine

Nitrous oxide has been used in dentistry and surgery, as an anaesthetic and analgesic, since 1844.^[27] In the early days, the gas was administered through simple inhalers consisting of a breathing bag made of rubber cloth.^[28] Today, the gas is administered in hospitals by means of an automated relative analgesia machine, with an anaesthetic vaporiser and a medical ventilator, that delivers a precisely dosed and breath-actuated flow of nitrous oxide mixed with oxygen in a 2:1 ratio.

Nitrous oxide is a weak general anaesthetic, and so is generally not used alone in general anaesthesia, but used as a carrier gas (mixed with oxygen) for more powerful general anaesthetic drugs such as sevoflurane or desflurane. It has a minimum alveolar concentration of 105% and a blood/gas partition coefficient of 0.46. The use of nitrous oxide in anaesthesia can increase the risk of postoperative nausea and vomiting.^[29][30][31]

Dentists use a simpler machine which only delivers an N
₂O/O
₂ mixture for the patient to inhale while conscious but must still be a recognised purpose designed dedicated relative analgesic flowmeter with a minimum 30% of oxygen at all times and a maximum upper limit of 70% nitrous oxide. The patient is kept conscious throughout the procedure, and retains adequate mental faculties to respond to questions and instructions from the dentist.^[32]

Inhalation of nitrous oxide is used frequently to relieve pain associated with childbirth, trauma, oral surgery and acute coronary syndrome (including heart attacks). Its use during labour has been shown to be a safe and effective aid for birthing women.^[33] Its use for acute coronary syndrome is of unknown benefit.^[34]

In Canada and the UK, Entonox and Nitronox are used commonly by ambulance crews (including unregistered practitioners) as rapid and highly effective analgesic gas.

Fifty per cent nitrous oxide can be considered for use by trained non-professional first aid responders in prehospital settings, given the relative ease and safety of administering 50% nitrous oxide as an analgesic. The rapid reversibility of its effect would also prevent it from precluding diagnosis.^[35]

Recreational use

Recreational inhalation of nitrous oxide, with the purpose of causing euphoria and/or slight hallucinations, began as a phenomenon for the British upper class in 1799, known as "laughing gas parties".^[36]

Starting in the 19th century, the widespread availability of the gas for medical and culinary purposes allowed for recreational use to expand greatly globally. In the UK as of 2014, nitrous oxide was estimated to be used by almost half a million young people at nightspots, festivals and parties.^[37]

Widespread recreational use of the drug throughout the UK was featured in the 2017 Vice documentary Inside The Laughing Gas Black Market, in which journalist Matt Shea met with dealers of the drug who stole it from hospitals.^[38]

A significant issue cited in London's press is the effect of nitrous oxide canister littering, which is highly visible and causes significant complaints from communities.^[39]

Prior to 8 November 2023, nitrous oxide was subject to the Psychoactive Substances Act 2016 in the UK. It was already illegal to produce, supply, import or export nitrous oxide for recreational use. However, the UK government updated the law on 8 November 2023 to include possession of nitrous oxide by classifying it as a Class C drug under the Misuse of Drugs Act 1971.^[40]

While casual use of nitrous oxide is understood by most recreational users to be a route to a "safe high", many are unaware that excessive consumption has the potential to cause neurological harm which, if left untreated, can result in permanent neurological damage.^[41] In Australia, recreation use became a public health concern following a rise in reported cases of neurotoxicity and a rise in emergency room admissions, and in (the state of) South Australia legislation was passed in 2020 to restrict canister sales.^[42]

Safety

Zdroj:https://en.wikipedia.org?pojem=Nitrous_oxide
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