The N-methyl-D-aspartate receptor, is a glutamate receptor and ion channel protein found in nerve cells. It is activated when glutamate and glycine bind to it, the NMDA receptor is very important for controlling synaptic plasticity and memory function. The NMDAR is a type of ionotropic glutamate receptor. The NMDA receptor is named this because the agonist molecule N-methyl-D-aspartate binds selectively to it, activation of NMDA receptors results in the opening of an ion channel that is nonselective to cations, with a reversal potential near 0 mV. While the opening and closing of the ion channel is primarily gated by ligand binding, extracellular magnesium and zinc ions can bind to specific sites on the receptor, blocking the passage of other cations through the open ion channel. Ca2+ flux through NMDARs is thought to be critical in synaptic plasticity, the opening and closing of the NMDA receptor is complex. While it is primarily a ligand-gated channel, it does display weaker voltage-dependence modulation of the ligand-dependent gating, the ligand gating requires co-activation by two ligands and either D-serine or glycine.
The voltage-dependence of current through the channel is due to binding of Mg2+ or Zn2+ ions to the protein as described above. The activity of the NMDA receptor is affected by many drugs such as phencyclidine, alcohol. The anaesthetic effects of the drugs ketamine and nitrous oxide are partially because of their effects on NMDA receptor activity, the NMDA receptor forms a heterotetramer between two GluN1 and two GluN2 subunits, two obligatory NR1 subunits and two regionally localized NR2 subunits. A related gene family of NR3 A and B subunits have an effect on receptor activity. Multiple receptor isoforms with distinct brain distributions and functional properties arise by selective splicing of the NR1 transcripts, NR1 subunits bind the co-agonist glycine and NR2 subunits bind the neurotransmitter glutamate. The agonist-binding module links to a domain, which consists of three transmembrane segments and a re-entrant loop reminiscent of the selectivity filter of potassium channels. The membrane domain contributes residues to the pore and is responsible for the receptors high-unitary conductance, high-calcium permeability.
This has revealed a common fold with amino acid-binding bacterial proteins, there are eight variants of the NR1 subunit produced by alternative splicing of GRIN1, NR1-1a, NR1-1b, NR1-1a is the most abundantly expressed form. Strong evidence shows that the genes encoding the NR2 subunits in vertebrates have undergone at least two rounds of gene duplication and they contain the binding-site for the neurotransmitter glutamate. More importantly, each NR2 subunit has a different intracellular C-terminal domain that can interact with different sets of signalling molecules, unlike NR1 subunits, NR2 subunits are expressed differentially across various cell types and control the electrophysiological properties of the NMDA receptor. One particular subunit, NR2B, is present in immature neurons and in extrasynaptic locations
Nitrous oxide, commonly known as laughing gas or nitrous, is a chemical compound, an oxide of nitrogen with the formula N 2O. At room temperature, it is a colorless, odorless non-flammable gas, at elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen. Nitrous oxide has significant medical uses, especially in surgery and dentistry and its name laughing gas is due to the euphoric effects of inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is used as an oxidizer in rocket propellants, Nitrous oxide occurs in small amounts in the atmosphere, but has been found recently to be a major scavenger of stratospheric ozone, with impact comparable to that of CFCs. It is estimated that 30% of the N 2O in the atmosphere is the result of human activity, Nitrous oxide can be used as an oxidizer in a rocket motor. This has the advantages over other oxidisers in that it is not only non-toxic, as a secondary benefit it can be readily decomposed to form breathing air.
Its high density and low storage pressure enable it to be competitive with stored high-pressure gas systems. In a 1914 patent, American rocket pioneer Robert Goddard suggested nitrous oxide, Nitrous oxide has been the oxidiser of choice in several hybrid rocket designs. The combination of nitrous oxide with hydroxyl-terminated polybutadiene fuel has been used by SpaceShipOne and it is notably used in amateur and high power rocketry with various plastics as the fuel. Nitrous oxide can 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. Because of the heat release, the catalytic action rapidly becomes secondary as thermal autodecomposition becomes dominant. In a vacuum thruster, this can provide a monopropellant specific impulse of as much as 180 s, while noticeably less than the Isp available from hydrazine thrusters, the decreased toxicity makes nitrous oxide an option worth investigating.
Nitrous oxide is said to deflagrate somewhere around 600 °C at a pressure of 21 atmospheres, at 600 psi for example, the required ignition energy is only 6 joules, whereas N 2O at 130 psi a 2500-joule ignition energy input is insufficient. In vehicle racing, nitrous oxide allows the engine to burn more fuel by providing more oxygen than air alone, the gas itself is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures. Therefore, it is mixed with another fuel that is easier to deflagrate. Nitrous oxide is a strong oxidant roughly equivalent to hydrogen peroxide, Nitrous oxide is sometimes injected into the intake manifold, whereas other systems directly inject right before the cylinder to increase power. The technique was used during World War II by Luftwaffe aircraft with the GM-1 system to boost the output of aircraft engines. Originally meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, accordingly, it was only used by specialized planes like high-altitude reconnaissance aircraft, high-speed bombers, and high-altitude interceptor aircraft
Lithium aluminium hydride
Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula LiAlH4. It was discovered by Finholt and Schlesinger in 1947 and this compound is used as a reducing agent in organic synthesis, especially for the reduction of esters, carboxylic acids, and amides. The solid is dangerously reactive toward water, releasing gaseous hydrogen, some related derivatives have been discussed for hydrogen storage. LAH is a solid, but commercial samples are usually gray due to contamination. This material can be purified by recrystallization from diethyl ether, large-scale purifications employ a Soxhlet extractor. Commonly, the impure gray material is used in synthesis, since the impurities are innocuous, the pure powdered material is pyrophoric, but not its large crystals. Some commercial materials contain mineral oil to inhibit reactions with atmospheric moisture, LAH violently reacts with water, including atmospheric moisture. The reaction proceeds according to the following idealized equation, LiAlH4 +4 H2O → LiOH + Al3 +4 H2 This reaction provides a method to generate hydrogen in the laboratory.
Aged, air-exposed samples often appear white because they have absorbed enough moisture to generate a mixture of the white compounds lithium hydroxide, LAH crystallizes in the monoclinic space group P21/c. The unit cell has the dimensions, a =4.82, b =7.81, in the structure, Li+ centers are surrounded by five AlH−4 tetrahedra. The Li+ centers are bonded to one atom from each of the surrounding tetrahedra creating a bipyramid arrangement. At high pressures a phase transition may occur to give β-LAH, LiCl is removed by filtration from an ethereal solution of LiAH, with subsequent precipitation of LiAH to yield a product containing around 1% w/w LiCl. LAH is soluble in many ethereal solutions, however, it may spontaneously decompose due to the presence of catalytic impurities, though, it appears to be more stable in tetrahydrofuran. Thus, THF is preferred over, e. g. diethyl ether, the table summarizes thermodynamic data for LAH and reactions involving LAH, in the form of standard enthalpy and Gibbs free energy change, respectively.
LAH is metastable at room temperature, during prolonged storage it slowly decomposes to Li3AlH6 and LiH. This process can be accelerated by the presence of elements, such as titanium. At about 200 °C, Li3AlH6 decomposes into LiH and Al which subsequently convert into LiAl above 400 °C, r3 is reversible with an equilibrium pressure of about 0.25 bar at 500 °C. R1 and R2 can occur at room temperature with suitable catalysts, lithium aluminium hydride is widely used in organic chemistry as a reducing agent
Halothane, sold under the brandname Fluothane among others, is a general anesthetic. It can be used to start or maintain anaesthesia, one of its benefits is that it does not increase the production of saliva which can be particularly useful in those who are difficult to intubate. Side effects include an irregular heartbeat, decreased effort to breathe and it should not be used in people with porphyria or a history of malignant hyperthermia either in themselves or their family members. It is unclear whether use during pregnancy is harmful to the baby, halothane is a chiral molecule that is used as a racemic mixture. It is on the World Health Organizations List of Essential Medicines, as of 2014 the wholesale cost in the developing world is about 22 to 52 USD for a 250 ml bottle. Its use in developed countries has been replaced by newer agents such as sevoflurane. It is no commercially available in the United States. It is a potent anesthetic with a MAC of 0. 74% and its blood/gas partition coefficient of 2.4 makes it an agent with moderate induction and recovery time.
It is not a good analgesic and its muscle relaxation effect is moderate, in rare cases, repeated exposure to halothane in adults was noted to result in severe liver injury. This occurred in one in 10,000 exposures. The resulting syndrome was referred to as halothane hepatitis, and is thought to result from the metabolism of halothane to trifluoroacetic acid via oxidative reactions in the liver, about 20% of inhaled halothane is metabolized by the liver and these products are excreted in the urine. The hepatitis syndrome had a mortality rate of 30% to 70%, concern for hepatitis resulted in a dramatic reduction in the use of halothane for adults and it was replaced in the 1980s by enflurane and isoflurane. By 2005, the most common volatile anesthetics used were isoflurane, however, by 2000, excellent for inhalation induction, had largely replaced the use of halothane in children. Halothane sensitises the heart to catecholamines, so it is liable to cause cardiac arrhythmias, occasionally fatal and this seems to be especially problematic in dental anaesthesia.
Like all the potent inhalational agents, it is a potent trigger for malignant hyperthermia. Similarly, in common with the potent inhalational agents, it relaxes uterine smooth muscle. People can be exposed to halothane in the workplace by breathing it in as waste gas, skin contact, eye contact. The National Institute for Occupational Safety and Health has set a recommended limit of 2 ppm over 60 minutes
An inhalational anaesthetic is a chemical compound possessing general anaesthetic properties that can be delivered via inhalation. They are administered by anaesthetists through a mask, laryngeal mask airway or tracheal tube connected to an anaesthetic vaporiser. All of these share the property of being quite hydrophobic. The ideal volatile anaesthetic agent offers smooth and reliable induction and maintenance of general anaesthesia with minimal effects on other organ systems. In addition it is odourless or pleasant to inhale, safe for all ages and in pregnancy, not metabolised, rapid in onset and offset, none of the agents currently in use are ideal, although many have some of the desirable characteristics. For example, sevoflurane is pleasant to inhale and is rapid in onset and offset and it is safe for all ages. However, it is expensive, and approximately half as potent as isoflurane, other gases or vapors which produce general anaesthesia by inhalation include nitrous oxide and xenon. These are stored in gas cylinders and administered using flowmeters, rather than vaporisers, cyclopropane is explosive and is no longer used for safety reasons, although otherwise it was found to be an excellent anaesthetic.
Xenon is odourless and rapid in onset, but is expensive and requires specialized equipment to administer, under hyperbaric conditions, other gases such as nitrogen, and noble gases such as argon and xenon become anaesthetics. When inhaled at high pressures, nitrogen begins to act as an anaesthetic agent. However, the minimum alveolar concentration for nitrogen is not achieved until pressures of about 20 to 30 atm are attained, argon is slightly more than twice as anaesthetic as nitrogen per unit of partial pressure. Xenon however is an anaesthetic at 80% concentration and normal atmospheric pressure. The full mechanism of action of volatile anaesthetic agents is unknown and has been the subject of intense debate. Anesthetics have been used for 160 years, and how work is one of the great mysteries of neuroscience, says anaesthesiologist James Sonner of the University of California. Anaesthesia research has been for a time a science of untestable hypotheses, notes Neil L. Harrison of Cornell University.
Most of the injectable anesthetics appear to act on a molecular target. It looks like inhaled anesthetics act on multiple molecular targets and that makes it a more difficult problem to pick apart. However, the agent may bind to a receptor with a weak interaction, a physical interaction such as swelling of nerve cell membranes from gas solution in the lipid bilayer may be operative
Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, odorless gas found in the Earths atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser used a xenon dimer molecule as the lasing medium. Xenon is used to search for hypothetical weakly interacting massive particles, naturally occurring xenon consists of eight stable isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135, and is the most significant neutron absorber in nuclear reactors, Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers in September 1898, shortly after their discovery of the elements krypton and neon.
They found xenon in the left over from evaporating components of liquid air. Ramsay suggested the name xenon for this gas from the Greek word ξένον, neuter singular form of ξένος, meaning foreign, strange, in 1902, Ramsay estimated the proportion of xenon in the Earths atmosphere to be one part in 20 million. During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography and this led him to the invention of the xenon flash lamp in which light is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method, in 1939, American physician Albert R. Behnke Jr. began exploring the causes of drunkenness in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, from his results, he deduced that xenon gas could serve as an anesthetic. Xenon was first used as an anesthetic in 1951 by American anesthesiologist Stuart C.
Cullen, who used it with two patients. Xenon and the noble gases were for a long time considered to be completely chemically inert. Since O2 and xenon have almost the same first ionization potential, on March 23,1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate. Bartlett thought its composition to be Xe+−, but revealed that it was probably a mixture of various xenon-containing salts. By 1971, more than 80 xenon compounds were known, in November 1989, IBM scientists demonstrated a technology capable of manipulating individual atoms
Potassium carbonate is a white salt, soluble in water which forms a strongly alkaline solution. It can be made as the product of potassium hydroxides absorbent reaction with carbon dioxide and it is deliquescent, often appearing a damp or wet solid. Potassium carbonate is used in the production of soap and glass, Potassium carbonate is the primary component of potash and the more refined pearl ash or salts of tartar. Historically, pearl ash was created by baking potash in a kiln to remove impurities, the fine, white powder remaining was the pearl ash. The first patent issued by the US Patent Office was awarded to Samuel Hopkins in 1790 for a method of making potash. In late 18th century North America, before the development of baking powder, potassium carbonate is prepared commercially by the electrolysis of potassium chloride. The resulting potassium hydroxide is carbonated using carbon dioxide to form potassium carbonate, 2KOH + CO2 → K2CO3 + H2O for soap and china production as a mild drying agent where other drying agents, such as calcium chloride and magnesium sulfate, may be incompatible.
It is not suitable for acidic compounds, but can be useful for drying an organic phase if one has an amount of acidic impurity. It may be used to dry some ketones, alcohols, in cuisine, where it has many traditional uses. It is an ingredient in the production of grass jelly, a food consumed in Chinese and Southeast Asian cuisines, as well as Chinese noodles and it is used to tenderize tripe. German gingerbread recipes often use potassium carbonate as a baking agent and it is however important that the right quantities are used to prevent harm, and cooks should not use it without guidance. In the production of powder to balance the pH of natural cocoa beans. As a fire suppressant in extinguishing deep-fat fryers and various other B class-related fires, in condensed aerosol fire suppression, although as the byproduct of potassium nitrate. As an ingredient in welding fluxes, and in the coating on arc-welding rods. as an aid to stability in neurons helping to maintain equilibrium. As an animal feed ingredient to satisfy the requirements of farmed animals such as broiler breeders.
A Dictionary of Science, Oxford University Press, New York,2004 International Chemical Safety Card 1588
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In organic chemistry, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group. The simplest of the class is phenol, which is called carbolic acid C 6H 5OH, phenolic compounds are classified as simple phenols or polyphenols based on the number of phenol units in the molecule. Synonyms are arenols or aryl alcohols, phenolic compounds are synthesized industrially, they are produced by plants and microorganisms, with variation between and within species. Although similar to alcohols, phenols have unique properties and are not classified as alcohols and they have higher acidities due to the aromatic rings tight coupling with the oxygen and a relatively loose bond between the oxygen and hydrogen. The acidity of the group in phenols is commonly intermediate between that of aliphatic alcohols and carboxylic acids. Phenols can have two or more hydroxy groups bonded to the ring in the same molecule. The simplest examples are the three benzenediols, each having two groups on a benzene ring.
Organisms that synthesize phenolic compounds do so in response to pressures such as pathogen and insect attack, UV radiation. As they are present in food consumed in human diets and in used in traditional medicine of several cultures, their role in human health. Some phenols are germicidal and are used in formulating disinfectants, others possess estrogenic or endocrine disrupting activity. They can be classified on the basis of their number of phenol groups and they can therefore be called simple phenols or monophenols, with only one phenolic group, or di-, tri- and oligophenols, with two, three or several phenolic groups respectively. The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol, two natural phenols from two different categories, for instance a flavonoid and a lignan, can combine to form a hybrid class like the flavonolignans. Nomenclature of polymers, Plants in the genus Humulus and Cannabis produce terpenophenolic metabolites, phenolic lipids are long aliphatic chains bonded to a phenolic moiety.
The majority of compounds are solubles molecules but the smaller molecules can be volatiles. Many natural phenols present chirality within their molecule, an example of such molecules is catechin. Cavicularin is an unusual macrocycle because it was the first compound isolated from nature displaying optical activity due to the presence of planar chirality, natural phenols chemically interact with many other substances. Stacking, a property of molecules with aromaticity, is seen occurring between phenolic molecules. When studied in mass spectrometry, phenols easily form adduct ions with halogens and they can interact with the food matrices or with different forms of silica
A psychoactive drug, psychopharmaceutical, or psychotropic is a chemical substance that changes brain function and results in alterations in perception, mood, or consciousness. These substances may be used recreationally, to alter ones consciousness, or, as entheogens, for ritual, spiritual, or shamanic purposes. Some categories of drugs, which have medical therapeutic value, are prescribed by medical doctors. There are some psychoactive substances used in the detoxification and rehabilitation programs for drug users. Psychoactive substances often bring about changes in consciousness and mood that the user may find rewarding. In addition, sustained use of some substances may produce a physical dependence or psychological dependence syndrome associated with somatic or psychological-emotional withdrawal states respectively, Drug rehabilitation aims to break this cycle of dependency, through a combination of psychotherapy, support groups and even other psychoactive substances. However, the reverse is true in some cases, that certain experiences on drugs may be so unfriendly.
This is especially true of certain deliriants, powerful dissociatives, and classic psychedelics, in part because of this potential for substance misuse, addiction, or dependence, the ethics of drug use is debated. Restrictions on drug production and sales in an attempt to drug abuse are very common among national and sub-national governments worldwide. Ethical concerns have raised about over-use of these drugs clinically. Psychoactive drug use can be traced to prehistory, there is archaeological evidence of the use of psychoactive substances dating back at least 10,000 years, and historical evidence of cultural use over the past 5,000 years. The chewing of coca leaves, for example, dates back over 8,000 years ago in Peruvian society, medicinal use is one important facet of psychoactive drug usage. However, some have postulated that the urge to alter ones consciousness is as primary as the drive to satiate thirst, hunger or sexual desire. Supporters of this belief contend that the history of use and even childrens desire for spinning, swinging.
It is, necessary to precisely what is meant by the use of drugs. We do not mean the purely physical craving, but there are not many drugs which have the power of stilling such craving. This relationship is not limited to humans, a number of animals consume different psychoactive plants, animals and even fermented fruit, becoming intoxicated, such as cats after consuming catnip. Traditional legends of sacred plants often contain references to animals that introduced humankind to their use and psychoactive plants appear to have co-evolved, possibly explaining why these chemicals and their receptors exist within the nervous system
Diethyl ether or simply ether, is an organic compound in the ether class with the formula 2O. It is a colorless, highly flammable liquid. It is commonly used as a solvent in laboratories and as a fluid for some engines. It was formerly used as an anesthetic, until non-flammable drugs were developed. It has been used as a drug to cause intoxication. The compound may have created by either Jābir ibn Hayyān in the 8th century or Ramon Llull in 1275. At about the time, Paracelsus discovered ethers analgesic properties in chickens. The name ether was given to the substance in 1729 by August Sigmund Frobenius and it is particularly important as a solvent in the production of cellulose plastics such as cellulose acetate. Ether starting fluid is sold and used in countries with cold climates, for the same reason it is used as a component of the fuel mixture for carbureted compression ignition model engines. In this way diethyl ether is very similar to one of its precursors, diethyl ether is a common laboratory aprotic solvent.
It has limited solubility in water and dissolves 1.5 g/100 ml water at 25 °C and this, coupled with its high volatility, makes it ideal for use as the non-polar solvent in liquid-liquid extraction. When used with a solution, the diethyl ether layer is on top due to the fact that it has a lower density than the water. It is a solvent for the Grignard reaction in addition to other reactions involving organometallic reagents. Morton participated in a demonstration of ether anesthesia on October 16,1846 at the Ether Dome in Boston. British doctors were aware of the properties of ether as early as 1840 where it was widely prescribed in conjunction with opium. Because of its associations with Boston, the use of ether became known as the Yankee Dodge, diethyl ether depresses the myocardium and increases tracheobronchial secretions. Diethyl ether could be mixed with other agents such as chloroform to make C. E. mixture, or chloroform. In the 2000s, ether is rarely used, the use of flammable ether was displaced by nonflammable fluorinated hydrocarbon anesthetics
Chloroform, or trichloromethane, is an organic compound with formula CHCl3. It is a colorless, sweet-smelling, dense liquid that is produced on a scale as a precursor to PTFE. It is a precursor to various refrigerants and it is one of the four chloromethanes and a trihalomethane. The molecule adopts tetrahedral molecular geometry with C3v symmetry, the total global flux of chloroform through the environment is approximately 7005660000000000000♠660000 tonnes per year, and about 90% of emissions are natural in origin. Many kinds of seaweed produce chloroform, and fungi are believed to produce chloroform in soil and its half-life in air ranges from 55 to 620 days. Biodegradation in water and soil is slow, chloroform does not significantly bioaccumulate in aquatic organisms. Justus von Liebig carried out the cleavage of chloral. Eugène Soubeiran obtained the compound by the action of chlorine bleach on both ethanol and acetone, in 1834, French chemist Jean-Baptiste Dumas determined chloroforms empirical formula and named it.
In 1835, Dumas prepared the substance by the cleavage of trichloroacetic acid. Regnault prepared chloroform by chlorination of chloromethane, in 1842 Dr Robert Mortimer Glover in London discovered the anaesthetic qualities of chloroform on laboratory animals. In 1847, Scottish obstetrician James Y. Simpson was the first to demonstrate the properties of chloroform on humans. By the 1850s, chloroform was being produced on a basis by using the Liebig procedure. Today, chloroform — along with dichloromethane — is prepared exclusively, in industry, chloroform is produced by heating a mixture of chlorine and either chloromethane or methane. CDCl3 is a solvent used in NMR spectroscopy. Deuterochloroform is produced by the reaction, the reaction of acetone with sodium hypochlorite or calcium hypochlorite. The haloform process is now obsolete for the production of ordinary chloroform, deuterochloroform can be prepared by the reaction of sodium deuteroxide with chloral hydrate, or from ordinary chloroform.
The haloform reaction can occur inadvertently in domestic settings, bleaching with hypochlorite generates halogenated compounds in side reactions, chloroform is the main byproduct. Chlorodifluoromethane is converted into tetrafluoroethylene, the precursor to Teflon