In chemistry, an ethyl group is an alkyl substituent derived from ethane. It has the formula –CH2CH3 and is often abbreviated Et. Ethyl is used in the IUPAC nomenclature of organic chemistry for a saturated two-carbon moiety in a molecule, whilst the prefix "eth-" is used to indicate the presence of two carbon atoms in the molecule. Ethylation is the formation of a compound by introduction of the ethyl group; the most practiced example of this reaction is the ethylation of benzene with ethylene to yield ethylbenzene, a precursor to styrene, a precursor to polystyrene. 24.7 million tons of ethylbenzene were produced in 1999. Many ethyl-containing compounds are generated by electrophilic ethylation, i.e. treatment of nucleophiles with sources of Et+. Triethyloxonium tetrafluoroborate BF4 is such a reagent. For good nucleophiles, less electrophilic reagents are employed, such as ethyl halides. In unsymmetrical ethylated compounds, the methylene protons in the ethyl substituent are diastereotopic. Chiral reagents are known to stereoselectively modify such substituents.
The name of the group is derived from the Aether, the first-born Greek elemental god of air and "hyle", referring to "stuff". The name "ethyl" was coined in 1835 by the Swedish chemist Jöns Jacob Berzelius. Functional group
In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula −C4H9, derived from either of the two isomers of butane. The isomer n-butane can connect in two ways, giving rise to two "-butyl" groups: If it connects at one of the two terminal carbon atoms, it is normal butyl or n-butyl: CH3−CH2−CH2−CH2− If it connects at one of the non-terminal carbon atoms, it is secondary butyl or sec-butyl: CH3−CH2−CH− The second isomer of butane, can connect in two ways, giving rise to two additional groups: If it connects at one of the three terminal carbons, it is isobutyl: 2CH−CH2− If it connects at the central carbon, it is tertiary butyl, tert-butyl or t-butyl: 3C− According to IUPAC nomenclature, "isobutyl", "sec-butyl", "tert-butyl" used to be allowed retained names; the latest guidance changed that: only tert-butyl is kept as preferred prefix, all other butyl-names are removed. In the convention of skeletal formulas, every line ending and line intersection specifies a carbon atom saturated with single-linked hydrogen atoms.
The "R" symbol indicates any other non-specific functional group. Butyl is the largest substituent for which trivial names are used for all isomers; the butyl group's carbon, connected to the rest of the molecule is called the RI or R-prime carbon. The prefixes sec and tert refer to the number of additional side chains connected to the first butyl carbon; the prefix "iso" means "equal" while the prefix'n-' stands for "normal". The four isomers of "butyl acetate" demonstrate these four isomeric configurations. Here, the acetate radical appears in each of the positions where the "R" symbol is used in the chart above: Alkyl radicals are considered as a series, a progression sequenced by the number of carbon atoms involved. In that progression, Butyl is the fourth, the last to be named for its history; the word "butyl" is derived from butyric acid, a four-carbon carboxylic acid found in rancid butter. The name "butyric acid" comes from butter. Subsequent alkyl radicals in the series are named from the Greek number that indicates the number of carbon atoms in the group: pentyl, heptyl, etc.
The tert-butyl substituent is bulky and is used in chemistry for kinetic stabilization, as are other bulky groups such as the related trimethylsilyl group. The effect of the tert-butyl group on the progress of a chemical reaction is called the tert-butyl effect, illustrated in the Diels-Alder reaction below. Compared to a hydrogen substituent, the tert-butyl substituent accelerates the reaction rate by a factor of 240; the tert-butyl effect is an example of steric hindrance
An allylic rearrangement or allylic shift is an organic reaction in which the double bond in an allyl chemical compound shifts to the next carbon atom. It is encountered in nucleophilic substitution. In reaction conditions that favor a SN1 reaction mechanism the intermediate is a carbocation for which several resonance structures are possible; this explains the product distribution after recombination with nucleophile Y. This type of process is called an SN1' substitution. Alternatively, it is possible for nucleophile to attack directly at the allylic position, displacing the leaving group in a single step, in a process referred to as SN2' substitution; this is in cases when the allyl compound is unhindered, a strong nucleophile is used. The products will be similar to those seen with SN1' substitution, thus reaction of 1-chloro-2-butene with sodium hydroxide gives a mixture of 2-buten-1-ol and 3-buten-2-ol: Nevertheless, the product in which the OH group is on the primary atom is minor. In the substitution of 1-chloro-3-methyl-2-butene, the secondary 2-methyl-3-buten-2-ol is produced in a yield of 85%, while that for the primary 3-methyl-2-buten-1-ol is 15%.
In one reaction mechanism the nucleophile attacks not directly at the electrophilic site but in a conjugate addition over the double bond: The synthetic utility can be extended to substitutions over butadiene bonds: Reaction in methanol and catalyst diisopropylethylamineIn the first step of this macrocyclization the thiol group in one end of 1,5-pentanedithiol reacts with the butadiene tail in 1 to the enone 2 in an allylic shift with a sulfone leaving group which reacts further with the other end in a conjugate addition reaction. In one study the allylic shift was applied twice in a ring system: In this reaction sequence a Jacobson epoxidation adds an epoxy group to a diene which serves as the leaving group in reaction with the pyrazole nucleophile; the second nucleophile is methylmagnesium bromide expulsing the pyrazole group. An SN2' reaction should explain the outcome of the reaction of an aziridine carrying a methylene bromide group with methyllithium: In this reaction one equivalent of acetylene is lost.
Examples of allylic shifts: Ferrier rearrangement Meyer–Schuster rearrangement In one adaptation called a SN2' reduction a formal organic reduction on an allyl group containing a good leaving group is accompanied by a rearrangement. One example of such reaction is found as part of a Taxol total synthesis: The hydride is lithium aluminium hydride and the leaving group a phosphonium salt; the product contains a new exocyclic double bond. Only when the cyclohexane ring is properly substituted will the proton add in a trans position with respect to the adjacent methyl group. A conceptually related reaction is the Whiting reaction forming dienes. Allyl shifts can take place with electrophiles. In the example below the carbonyl group in benzaldehyde is activated by diboronic acid prior to reaction with the allyl alcohol
Chemistry is the scientific discipline involved with elements and compounds composed of atoms and ions: their composition, properties and the changes they undergo during a reaction with other substances. In the scope of its subject, chemistry occupies an intermediate position between physics and biology, it is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry, the formation of igneous rocks, how atmospheric ozone is formed and how environmental pollutants are degraded, the properties of the soil on the moon, how medications work, how to collect DNA evidence at a crime scene. Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron; the word chemistry comes from alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, philosophy, astronomy and medicine.
It is seen as linked to the quest to turn lead or another common starting material into gold, though in ancient times the study encompassed many of the questions of modern chemistry being defined as the study of the composition of waters, growth, disembodying, drawing the spirits from bodies and bonding the spirits within bodies by the early 4th century Greek-Egyptian alchemist Zosimos. An alchemist was called a'chemist' in popular speech, the suffix "-ry" was added to this to describe the art of the chemist as "chemistry"; the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία; this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, in turn derived from the word Kemet, the ancient name of Egypt in the Egyptian language. Alternately, al-kīmīā may derive from χημεία, meaning "cast together"; the current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, molecules, metals and other aggregates of matter.
This matter can be studied in isolation or in combination. The interactions and transformations that are studied in chemistry are the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together; such behaviors are studied in a chemistry laboratory. The chemistry laboratory stereotypically uses various forms of laboratory glassware; however glassware is not central to chemistry, a great deal of experimental chemistry is done without it. A chemical reaction is a transformation of some substances into one or more different substances; the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which involves atoms as subjects; the number of atoms on the left and the right in the equation for a chemical transformation is equal. The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions, they can be analyzed using the tools of e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; the particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a mixture of substances; the atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud; the nucleus is made up of positively charged protons and uncharged neutrons, while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons.
The nucleus is dense. The atom is the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state, coordination number, preferred types of bonds to form. A chemical element is a pure substance, composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z; the mass number is the sum of the number of neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same
Hydrogen is a chemical element with symbol H and atomic number 1. With a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table. Hydrogen is the most abundant chemical substance in the Universe, constituting 75% of all baryonic mass. Non-remnant stars are composed of hydrogen in the plasma state; the most common isotope of hydrogen, termed protium, has no neutrons. The universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, tasteless, non-toxic, nonmetallic combustible diatomic gas with the molecular formula H2. Since hydrogen forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays a important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge when it is known as a hydride, or as a positively charged species denoted by the symbol H+.
The hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics. Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, that it produces water when burned, the property for which it was named: in Greek, hydrogen means "water-former". Industrial production is from steam reforming natural gas, less from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production for the fertilizer market. Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks.
Hydrogen gas is flammable and will burn in air at a wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol: 2 H2 + O2 → 2 H2O + 572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74% and with chlorine at 5–95%; the explosive reactions may be triggered by heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C. Pure hydrogen-oxygen flames emit ultraviolet light and with high oxygen mix are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine, compared to the visible plume of a Space Shuttle Solid Rocket Booster, which uses an ammonium perchlorate composite; the detection of a burning hydrogen leak may require a flame detector. Hydrogen flames in other conditions are blue; the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a rich mixture of hydrogen to oxygen combined with carbon compounds from the airship skin.
H2 reacts with every oxidizing element. Hydrogen can react spontaneously and violently at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are potentially dangerous acids; the ground state energy level of the electron in a hydrogen atom is −13.6 eV, equivalent to an ultraviolet photon of 91 nm wavelength. The energy levels of hydrogen can be calculated accurately using the Bohr model of the atom, which conceptualizes the electron as "orbiting" the proton in analogy to the Earth's orbit of the Sun. However, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity; because of the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, therefore only certain allowed energies. A more accurate description of the hydrogen atom comes from a purely quantum mechanical treatment that uses the Schrödinger equation, Dirac equation or the Feynman path integral formulation to calculate the probability density of the electron around the proton.
The most complicated treatments allow for the small effects of special relativity and vacuum polarization. In the quantum mechanical treatment, the electron in a ground state hydrogen atom has no angular momentum at all—illustrating how the "planetary orbit" differs from electron motion. There exist two different spin isomers of hydrogen diatomic molecules that differ by the relative spin of their nuclei. In the orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1. At standard temperature and pressure, hydrogen gas contains about 25% of the para form and 75% of the ortho form known as the "normal form"; the equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but because the ortho form is an excited state and has a higher energy
Wine is an alcoholic drink made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol, carbon dioxide, heat. Different varieties of grapes and strains of yeasts produce different styles of wine; these variations result from the complex interactions between the biochemical development of the grape, the reactions involved in fermentation, the terroir, the production process. Many countries enact legal appellations intended to define qualities of wine; these restrict the geographical origin and permitted varieties of grapes, as well as other aspects of wine production. Wines not made from grapes include rice wine and fruit wines such as plum, pomegranate and elderberry. Wine has been produced for thousands of years; the earliest known traces of wine are from Georgia and Sicily although there is evidence of a similar alcoholic drink being consumed earlier in China. The earliest known winery is the 6,100-year-old Areni-1 winery in Armenia. Wine reached the Balkans by 4500 BC and was consumed and celebrated in ancient Greece and Rome.
Throughout history, wine has been consumed for its intoxicating effects. Wine has long played an important role in religion. Red wine was associated with blood by the ancient Egyptians and was used by both the Greek cult of Dionysus and the Romans in their Bacchanalia; the earliest archaeological and archaeobotanical evidence for grape wine and viniculture, dating to 6000–5800 BC was found on the territory of modern Georgia. Both archaeological and genetic evidence suggest that the earliest production of wine elsewhere was later having taken place in the Southern Caucasus, or the West Asian region between Eastern Turkey, northern Iran; the earliest evidence of a grape-based fermented drink was found in China, Georgia from 6000 BC, Iran from 5000 BC, Sicily from 4000 BC. The earliest evidence of a wine production facility is the Areni-1 winery in Armenia and is at least 6100 years old. A 2003 report by archaeologists indicates a possibility that grapes were mixed with rice to produce mixed fermented drinks in China in the early years of the seventh millennium BC.
Pottery jars from the Neolithic site of Jiahu, contained traces of tartaric acid and other organic compounds found in wine. However, other fruits indigenous to the region, such as hawthorn, cannot be ruled out. If these drinks, which seem to be the precursors of rice wine, included grapes rather than other fruits, they would have been any of the several dozen indigenous wild species in China, rather than Vitis vinifera, introduced there 6000 years later; the spread of wine culture westwards was most due to the Phoenicians who spread outward from a base of city-states along the Mediterranean coast of what are today Syria, Lebanon and Palestine. The wines of Byblos were exported to Egypt during the Old Kingdom and throughout the Mediterranean. Evidence includes two Phoenician shipwrecks from 750 BC discovered by Robert Ballard, whose cargo of wine was still intact; as the first great traders in wine, the Phoenicians seem to have protected it from oxidation with a layer of olive oil, followed by a seal of pinewood and resin, similar to retsina.
Although the nuragic Sardinians consumed wine before the arrival of the Phoenicians The earliest remains of Apadana Palace in Persepolis dating back to 515 BC include carvings depicting soldiers from Achaemenid Empire subject nations bringing gifts to the Achaemenid king, among them Armenians bringing their famous wine. Literary references to wine are abundant in Homer and others. In ancient Egypt, six of 36 wine amphoras were found in the tomb of King Tutankhamun bearing the name "Kha'y", a royal chief vintner. Five of these amphoras were designated as originating from the king's personal estate, with the sixth from the estate of the royal house of Aten. Traces of wine have been found in central Asian Xinjiang in modern-day China, dating from the second and first millennia BC; the first known mention of grape-based wines in India is from the late 4th-century BC writings of Chanakya, the chief minister of Emperor Chandragupta Maurya. In his writings, Chanakya condemns the use of alcohol while chronicling the emperor and his court's frequent indulgence of a style of wine known as madhu.
The ancient Romans planted vineyards near garrison towns so wine could be produced locally rather than shipped over long distances. Some of these areas are now world-renowned for wine production; the Romans discovered that burning sulfur candles inside empty wine vessels kept them fresh and free from a vinegar smell. In medieval Europe, the Roman Catholic Church supported wine because the clergy required it for the Mass. Monks in France made wine for years. An old English recipe that survived in various forms until the 19th century calls for refining white wine from bastard—bad or tainted bastardo wine; the English word "wine" comes from the Proto-Germanic *winam, an early borrowing from the Latin vinum, "wine" or " vine", itself derived from the Proto-Indo-European stem *win-o-. The earliest attested terms referring to wine are the Mycenaean Greek me-tu-wo ne-wo, meaning "in" or " of the new wine", wo-no-wa-ti-si, meaning "wine garden", written in Linear B inscriptions. Linear B includes, inter alia, an ideogram for wine
In organic chemistry, propargyl is an alkyl functional group of 2-propynyl with the structure HC≡C−CH2−, derived from the alkyne propyne. The term propargylic refers to a saturated position on a molecular framework next to an alkynyl group; the name comes from mix of propene and argentum, which refers to the typical reaction of the terminal alkynes with silver salts. The term homopropargylic designates in the same manner a saturated position on a molecular framework next to a propargylic group and thus two bonds from an alkyne moiety. A 3-butynyl fragment, HC ≡ C-CH2CH2-, or substituted homologue. Alkenyl groups Allyl Vinyl group Ethynyl Propargyl chloride Propargyl alcohol Propargyl bromide Propiolic acid