A mosquito coil is a mosquito-repelling incense made into a spiral, made using dried paste of pyrethrum powder. The coil is held at the center of the spiral, suspending it in the air, or wedged by two pieces of fireproof netting to allow continuous smoldering. Burning begins at the outer end of the spiral and progresses toward the center of the spiral, producing a mosquito-repellent smoke. A typical mosquito coil lasts around 7 -- 12 hours. Mosquito coils are used in Asia, South America and Australia. Pyrethrum was used for centuries as an insecticide in Persia and Europe, being developed into a mosquito coil in the late 1800s by a Japanese business man, Eiichiro Ueyama. At that time in Japan, pyrethrum powder was burned to repel mosquitoes. Ueyama created incense sticks mixed from starch powder, dried mandarin orange skin powder, pyrethrum powder, burning in around 40 minutes. In 1895, his wife Yuki proposed making the sticks thicker and longer, curling them in spirals, in order to make them last longer.
In 1902, after a series of trials and errors, he achieved an incense burning effect with a spiral shape. The method included cutting thick incense bars to a set length and manually winding them into a spiral; this method was used until 1957. After the Second World War, his company, Dainihon Jochugiku Co. Ltd, established joint-venture firms in various countries, including China and Thailand, to produce mosquito repelling products based on local conditions. Active ingredients found in mosquito coils may include: Pyrethrum – a natural, powdered material from a kind of chrysanthemum plant. Pyrethrins – an extract of the insecticidal chemicals in pyrethrum. Allethrin – sometimes d-trans-allethrin, the first synthetic pyrethroid. Esbiothrin – a form of allethrin. Meperfluthrin - a pyrethroid ester Butylated hydroxytoluene – an optional additive used to prevent pyrethroid from oxidizing during burning. Piperonyl butoxide – an optional additive to improve the effectiveness of pyrethroid. N-Octyl bicycloheptene dicarboximide – an optional additive to improve the effectiveness of a pyrethroid.
Dimefluthrin - a pyrethroid pesticide. Mosquito coils can be fire hazards, their use has resulted in numerous accidental fires. In 1999, a fire in a South Korean three-story dormitory caused the death of 23 people when a mosquito coil was left unattended; the strong smell from the smoke may linger, permeating fabric and furniture. Mosquito coils are considered to be safe insecticides for humans and mammals, although some studies highlight concerns when they are used in closed rooms. Coils sold in China and Malaysia were found to produce as much smoke PM2.5 as 75-137 burning cigarettes and formaldehyde emission levels in line with 51 burning cigarettes. Other studies in rats conclude that mosquito coils are not a significant health risk, although some organisms may experience temporary sensory irritation like that caused by smoke from the combustion of organic materials such as logs. In one study, rats were directly exposed to a coil's smoke for six hours a day, five days a week for thirteen weeks.
They showed signs of sensory irritation from the high smoke concentration, but there were no adverse effects on other parts of the body. The study concluded. Mosquito trap History of Dainihon Jochugiku Co. Ltd
A methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms — CH3. In formulas, the group is abbreviated Me; such hydrocarbon groups occur in many organic compounds. It is a stable group in most molecules. While the methyl group is part of a larger molecule, it can be found on its own in any of three forms: anion, cation or radical; the anion has the radical seven and the cation six. All three forms are reactive and observed; the methylium cation is otherwise not encountered. Some compounds are considered to be sources of the CH3+ cation, this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives a electrophilic methylating reagent: CH3OH + H+ → CH3+ + H2OSimilarly, methyl iodide and methyl triflate are viewed as the equivalent of the methyl cation because they undergo SN2 reactions by weak nucleophiles; the methanide anion exists only under exotic conditions. It can be produced by electrical discharge in ketene at low pressure and its enthalpy of reaction is determined to be about 252.2±3.3 kJ/mol.
In discussions mechanisms of organic reactions, methyl lithium and related Grignard reagents are considered to be salts of "CH3−". Such reagents are prepared from the methyl halides: 2 M + CH3X → MCH3 + MXwhere M is an alkali metal; the methyl radical has the formula CH3. It exists in dilute gases, but in more concentrated form it dimerizes to ethane, it can be produced by thermal decomposition of only certain compounds those with an -N=N- linkage. The reactivity of a methyl group depends on the adjacent substituents. Methyl groups can be quite unreactive. For example, in organic compounds, the methyl group resists attack by the strongest acids; the oxidation of a methyl group occurs in nature and industry. The oxidation products derived from methyl are CH2OH, CHO, CO2H. For example, permanganate converts a methyl group to a carboxyl group, e.g. the conversion of toluene to benzoic acid. Oxidation of methyl groups gives protons and carbon dioxide, as seen in combustion. Demethylation is a common process, reagents that undergo this reaction are called methylating agents.
Common methylating agents are dimethyl sulfate, methyl iodide, methyl triflate. Methanogenesis, the source of natural gas, arises via a demethylation reaction. Certain methyl groups can be deprotonated. For example, the acidity of the methyl groups in acetone is about 1020 more acidic than methane; the resulting carbanions are key intermediates in many reactions in organic synthesis and biosynthesis. Fatty acids are produced in this way; when placed in benzylic or allylic positions, the strength of the C-H bond is decreased, the reactivity of the methyl group increases. One manifestation of this enhanced reactivity is the photochemical chlorination of the methyl group in toluene to give benzyl chloride. In the special case where one hydrogen is replaced by deuterium and another hydrogen by tritium, the methyl substituent becomes chiral. Methods exist to produce optically pure methyl compounds, e.g. chiral acetic acid. Through the use of chiral methyl groups, the stereochemical course of several biochemical transformations have been analyzed.
A methyl group may rotate around the R—C-axis. This is a free rotation only in the simplest cases like gaseous CClH3. In most molecules, the remainder R breaks the C ∞ symmetry of the R—C-axis and creates a potential V that restricts the free motion of the three protons. For the model case of C2H6 this is discussed under the name ethane barrier. In condensed phases, neighbour molecules contribute to the potential. Methyl group rotation can be experimentally studied using quasielastic neutron scattering. French chemists Jean-Baptiste Dumas and Eugene Peligot, after determining methanol's chemical structure, introduced "methylene" from the Greek methy "wine" and hȳlē "wood, patch of trees" with the intention of highlighting its origins, "alcohol made from wood"; the term "methyl" was derived in about 1840 by back-formation from "methylene", was applied to describe "methyl alcohol". Methyl is the IUPAC nomenclature of organic chemistry term for an alkane molecule, using the prefix "meth-" to indicate the presence of a single carbon
Copper cyanide is an inorganic compound with the formula CuCN. This off-white solid occurs in two polymorphs; the compound is useful as a catalyst, in electroplating copper, as a reagent in the preparation of nitriles. Copper cyanide is a coordination polymer, it exists in two polymorphs both of which contain -- chains made from linear copper centres linked by cyanide bridges. In the high-temperature polymorph, HT-CuCN, isostructural with AgCN, the linear chains pack on a hexagonal lattice and adjacent chains are off set by +/- 1/3 c, Figure 1. In the low-temperature polymorph, LT-CuCN, the chains deviate from linearity and pack into rippled layers which pack in an AB fashion with chains in adjacent layers rotated by 49 °, Figure 2. LT-CuCN can be converted to HT-CuCN by heating to 563 K in an inert atmosphere. In both polymorphs the copper to carbon and copper to nitrogen bond lengths are ~1.85 Å and bridging cyanide groups show head-to-tail disorder. Cuprous cyanide is supplied as the low-temperature polymorph.
It can be prepared by the reduction of copper sulfate with sodium bisulfite at 60 °C, followed by the addition of sodium cyanide to precipitate pure LT-CuCN as a pale yellow powder. 2 CuSO4 + NaHSO3 + H2O + 2 NaCN → 2 CuCN + 3 NaHSO4On addition of sodium bisulfite the copper sulfate solution turns from blue to green, at which point the sodium cyanide is added. The reaction is performed under mildly acidic conditions. Copper cyanide has been prepared by treating copper sulfate with sodium cyanide, in this redox reaction, copper cyanide forms together with cyanogen: 2 CuSO4 + 4 NaCN → 2 CuCN + 2 + 2 Na2SO4Because this synthetic route produces cyanogen, uses two equivalents of sodium cyanide per equivalent of CuCN made and the resulting copper cyanide is impure it is not the industrial production method; the similarity of this reaction to that between copper sulfate and sodium iodide to form copper iodide is one example of cyanide ions acting as a pseudo halide. It explains why copper cyanide, Cu2, has not been synthesised.
Copper cyanide is insoluble in water but dissolves in solutions containing CN− to form 2− and 3−, which exhibit trigonal planar and tetrahedral coordination geometry, respectively. These complexes contrast with those of silver and gold cyanides, which form − ions in solution; the coordination polymer KCu2 contains − units. Copper cyanide is soluble in concentrated aqueous ammonia, pyridine and N-methylpyrrolidone. Cuprous cyanide is used for electroplating copper. CuCN is a prominent reagent in organocopper chemistry, it reacts with organolithium reagents to form "mixed cuprates" with the formulas Li and Li2. The use of CuCN revolutionized the deployment of simpler organocopper reagents of the type CuR and LiCuR2, the so-called Gilman reagents. In the presence of cyanide, these mixed cuprates are more purified and more stable; the mixed cuprates Li and Li2 function as sources of the carbanions R−, but with diminished reactivity compared to the parent organolithium reagent. Thus they are useful for some displacement reactions.
Addition of CuCN to CuCN forms silyl and stannyl reagents, which are used as sources of R3Si− and R3Sn−. CuCN is used in the conversion of aryl halides to nitriles. National Pollutant Inventory - Cyanide compounds fact sheet National Pollutant Inventory - Copper and compounds fact sheet
Paris green is an inorganic compound. It is a toxic emerald-green crystalline powder, used as a rodenticide and insecticide, as a pigment, despite its toxicity, it is used as a blue colorant for fireworks. The color of Paris green is said to range from a pale blue green when finely ground, to a deeper green when coarsely ground. Paris green may be prepared by combining arsenic trioxide. At the turn of the 20th century, Paris green, blended with lead arsenate, was used in America and elsewhere as an insecticide on produce such as apples; the toxic mixture is said "to have burned the trees and the grass around the trees". Paris green was sprayed by airplane in Italy and Corsica during 1944 and in Italy in 1945 to control malaria, it was once used to kill rats in Parisian sewers, how it acquired its common name. It was used in the Americas to control the tobacco budworm, Heliothis virescens. Paris green called emerald green, was a popular pigment used in artists' paints by the English painter W. Turner, Impressionists such as Monet and Renoir, Post-Impressionists such as Gauguin, Cézanne, Van Gogh.
Similar natural compounds are the minerals chalcophyllite Cu18Al23327·36H2O, conichalcite CaCu, cornubite Cu524·H2O, cornwallite Cu524·H2O, liroconite Cu2Al4·4H2O. These vivid minerals range from greenish blue to yellowish green. Scheele's green is a chemically simpler, less brilliant, less permanent, synthetic copper-arsenic pigment used for a rather short time before Paris green was first prepared, 1814, it would degrade, with moisture and molds, to arsine gas. Paris green may have been used in wallpaper to some extent and may have degraded similarly. Both pigments were once used in printing ink formulations; the ancient Romans used one of them conichalcite, as a green pigment. The Paris green paint used by the Impressionists is said to have been composed of coarse particles; the chemical was produced with small grinds and without removing impurities. It is that it was ground more finely for use in watercolors and inks, too. List of colors List of inorganic pigments Fiedler, I. and Bayard, M. A.
"Emerald Green and Scheele’s Green", in Artists' Pigments: A Handbook of Their History and Characteristics, Vol. 3: E. W. Fitzhugh Oxford University Press 1997, pp. 219–271 Hughes, Michael F.. "Arsenic Exposure and Toxicology: A Historical Perspective". Toxicological Sciences. 123: 305–332. Doi:10.1093/toxsci/kfr184. PMC 3179678. PMID 21750349. Sorensen, W. Conner. Brethren of the Net, American Entomology, 1840-1880. University of Alabama Press. Pp. 124–125. Spear, Robert J; the Great Gypsy Moth War, A History of the First Campaign in Massachusetts to Eradicate the Gypsy Moth, 1890-1901. University of Massachusetts Press and Boston, 2005. ISBN 1-55849-479-0 Case Studies in Environmental Medicine - Arsenic Toxicity How Emerald green is made National Pollutant Inventory - Copper and compounds fact sheet Emerald green, Colourlex
Mosquitoes are a group of about 3500 species of small insects that are a type of fly. Within that order they constitute the family Culicidae; the word "mosquito" is Spanish for "little fly". Mosquitoes have a slender segmented body, a pair of wings, three pairs of long hair-like legs, feathery antennae, elongated mouthparts. Mosquitoes diverged from other insects about 226 million years ago. Fossils of primitive mosquitoes have been found; the life cycle consists of the egg, larva and adult. Eggs are laid on the water surface. Females of most species have tube-like mouthparts which can pierce the skin of the host in order to extract blood, which contains protein and iron needed to produce eggs. Thousands of mosquito species feed on the blood of various hosts — vertebrates, including mammals, reptiles and some fish; this loss of blood is of any importance to the host. The saliva of the mosquito transmitted to the host with the bite can cause a rash. In addition, many species of mosquitoes inject or ingest disease-causing organisms with the bite and are thus a vector for the transmission of diseases such as malaria, yellow fever, West Nile virus, dengue fever, Zika virus and other arboviruses.
Mosquitoes kill more people than any other animal: over 700,000 each year. The oldest known mosquito with an anatomy similar to modern species was found in 79-million-year-old Canadian amber from the Cretaceous. An older sister species with more primitive features was found in Burmese amber, 90 to 100 million years old. Two mosquito fossils have been found that show little morphological change in modern mosquitoes against their counterpart from 46 million years ago; these fossils are the oldest found to have blood preserved within their abdomens. Despite no fossils being found earlier than the Cretaceous, recent studies suggest that the earliest divergence of mosquitoes between the lineages leading to Anophelinae and Culicinae occurred 226 million years ago; the mosquito Anopheles gambiae is undergoing speciation into the M and S molecular forms. Some pesticides that work on the M form no longer work on the S form. Over 3,500 species of the Culicidae have been described, they are divided into two subfamilies which in turn comprise some 43 genera.
These figures are subject to continual change, as more species are discovered, as DNA studies compel rearrangement of the taxonomy of the family. The two main subfamilies are the Anophelinae and Culicinae, with their genera as shown in the subsection below; the distinction is of great practical importance because the two subfamilies tend to differ in their significance as vectors of different classes of diseases. Speaking, arboviral diseases such as yellow fever and dengue fever tend to be transmitted by Culicine species, not in the genus Culex; some transmit various species of avian malaria, but it is not clear that they transmit any form of human malaria. Some species do however transmit various forms of filariasis, much as many Simuliidae do. Mosquitoes are members of a family of nematocerid flies: the Culicidae. Superficially, mosquitoes resemble. Anophelinae Culicinae Over 3,500 species of mosquitoes have thus far been described in the scientific literature. Like all flies, mosquitoes go through four stages in their lifecycles: egg, larva and adult or imago.
The first three stages—egg and pupa—are aquatic. These stages last 5 to 14 days, depending on the species and the ambient temperature, but there are important exceptions. Mosquitoes living in regions where some seasons are freezing or waterless spend part of the year in diapause. For instance, Wyeomyia larvae get frozen into solid lumps of ice during winter and only complete their development in spring; the eggs of some species of Aedes remain unharmed in diapause if they dry out, hatch when they are covered by water. Eggs hatch to become larvae; the adult mosquito emerges from the mature pupa. Bloodsucking mosquitoes, depending on species and weather conditions, have potential adult lifespans ranging from as short as a week to as long as several months; some species can overwinter as adults in diapause. In most species, adult females lay their eggs in stagnant water: some lay near the water's edge while others attach their eggs to aquatic plants; each species selects the situation of the water into which it lays its eggs and does so according to its own ecological adaptations.
Some are generalists and are not fussy. Some breed in some in temporary puddles; some breed in some in salt-marshes. Among those that breed in salt water, some are at home in fresh and salt water up to about one-third the concentration of seawater, whereas others must acclimatize themselves to the salinity; such differences are important because certain ecological pre
A carbamate is an organic compound derived from carbamic acid. A carbamate group, carbamate ester, carbamic acids are functional groups that are inter-related structurally and are interconverted chemically. Carbamate esters are called urethanes. Carbamic acids are unstable. For example, ammonium carbamate is generated by treatment of ammonia with carbon dioxide 2 NH3 + CO2 → NH4Carbamates arise via alcoholysis of chloroformamides: R2NCCl + R'OH → R2NCO2R' + HClAlternatively, cabamates can be formed from chloroformates and amines: R'OCCl + R2NH → R2NCO2R' + HClCarbamates may be formed from the Curtius rearrangement, where isocyanates formed are reacted with an alcohol. RCON3 → RNCO + N2 RNCO + R′OH → RNHCO2R′ Although most of this article concerns organic carbamates, the inorganic salt ammonium carbamate is produced on a large scale as an intermediate in the production of the commodity chemical urea from ammonia and carbon dioxide; the N-terminal amino groups of valine residues in the α- and β-chains of deoxyhemoglobin exist as carbamates.
They help to stabilise the protein, when it becomes deoxyhemoglobin and increases the likelihood of the release of remaining oxygen molecules bound to the protein. This stabilizing effect should not be confused with the Bohr effect; the ε-amino groups of the lysine residues in urease and phosphotriesterase feature carbamate. The carbamate derived from aminoimidazole is an intermediate in the biosynthesis of inosine. Carbamoyl phosphate is generated from carboxyphosphate rather than CO2; the most important carbamate is the one involved in the capture of CO2 by plants since this process is necessary for their growth. The enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase fixes a molecule of carbon dioxide as phosphoglycerate in the Calvin cycle. At the active site of the enzyme, a Mg2+ ion is bound to glutamate and aspartate residues as well as a lysine carbamate; the carbamate is formed when an uncharged lysine side chain near the ion reacts with a carbon dioxide molecule from the air, which renders it charged, therefore, able to bind the Mg2+ ion.
Some of the most common amine protecting groups, such as BOC, FMOC, Cbz and troc are carbamates. The so-called carbamate insecticides feature the carbamate ester functional group. Included in this group are aldicarb, carbaryl, fenobucarb and methomyl; these insecticides kill insects by reversibly inactivating the enzyme acetylcholinesterase. The organophosphate pesticides inhibit this enzyme, although irreversibly, cause a more severe form of cholinergic poisoning. Fenoxycarb has a carbamate group but acts as a juvenile hormone mimic, rather than inactivating acetylcholinesterase; the insect repellent icaridin is a substituted carbamate. Carbamate nerve agentsWhile the carbamate acetylcholinesterase inhibitors are referred to as "carbamate insecticides" due to their high selectivity for insect acetylcholinesterase enzymes over the mammalian versions, the most potent compounds such as aldicarb and carbofuran are still capable of inhibiting mammalian acetylcholinesterase enzymes at low enough concentrations that they pose a significant risk of poisoning to humans when used in large amounts for agricultural applications.
Other carbamate based acetylcholinesterase inhibitors are known with higher toxicity to humans, some such as T-1123 and EA-3990 were investigated for potential military use as nerve agents. However, since all compounds of this type have a quaternary ammonium group with a permanent positive charge, they have poor blood-brain barrier penetration, are only stable as crystalline salts or aqueous solutions, so were not considered to have suitable properties for weaponisation. Polyurethanes contain multiple carbamate groups as part of their structure; the "urethane" in the name "polyurethane" refers to these carbamate groups. In contrast, the substance called "urethane", ethyl carbamate, is neither a component of polyurethanes, nor is it used in their manufacture. Urethanes are formed by reaction of an alcohol with an isocyanate. Urethanes made by a non-isocyanate route are called carbamates. Polyurethane polymers have a wide range of properties and are commercially available as foams and solids. Polyurethane polymers are made by combining diisocyanates, e.g. toluene diisocyanate, diols, where the carbamate groups are formed by reaction of the alcohols with the isocyanates: RN=C=O + R′OH → RNHCOR′ Iodopropynyl butylcarbamate is a wood and paint preservative and used in cosmetics.
Urethane was once produced commercially in the United States as a chemotherapy agent and for other medicinal purposes. It was found to be toxic and ineffective, it is used as a veterinary medicine. In addition, some carbamates are used in human pharmacotherapy, for example, the acetylcholinesterase inhibitors neostigmine and rivastigmine, whose chemical structure is based on the natural alkaloid physostigmine. Other examples are meprobamate and its derivatives like carisoprodol, felbamate and tybamate, a class of anxiolytic and muscle relaxant drugs used in the 1960s before the rise of benzodiazepines, still used nowadays in some cases. Carbachol is used for various ophthalmic purposes; the protease inhibitor darunavir for HIV treatment contains a carbamate functional group. Carbamate insecticides target human melatonin receptors, along with inhibiting acetylcholi