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Chemical Shift
In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of an atomic nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure of a molecule. Chemical shifts are also used to describe signals in other forms of spectroscopy such as photoemission spectroscopy. Some atomic nuclei possess a magnetic moment (nuclear spin), which gives rise to different energy levels and resonance frequencies in a magnetic field. The total magnetic field experienced by a nucleus includes local magnetic fields induced by currents of electrons in the molecular orbitals (electrons have a magnetic moment themselves). The electron distribution of the same type of nucleus (e.g. ) usually varies according to the local geometry (binding partners, bond lengths, angles between bonds, and so on), and with it the local magnetic field at each nucleus. This is reflected in the spin energy levels (an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Magnetic Resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. High-resolution nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crysta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Magnetic Resonance Spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a Spectroscopy, spectroscopic technique based on re-orientation of Atomic nucleus, atomic nuclei with non-zero nuclear spins in an external magnetic field. This re-orientation occurs with absorption of electromagnetic radiation in the radio frequency region from roughly 4 to 900 MHz, which depends on the Isotope, isotopic nature of the nucleus and increases proportionally to the strength of the external magnetic field. Notably, the resonance frequency of each NMR-active nucleus depends on its chemical environment. As a result, NMR spectra provide information about individual functional groups present in the sample, as well as about connections between nearby nuclei in the same molecule. As the NMR spectra are unique or highly characteristic to individual compounds and functional groups, NMR spectroscopy is one of the most important methods to identify ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorine NMR
Fluorine-19 nuclear magnetic resonance spectroscopy (fluorine NMR or 19F NMR) is an analytical technique used to detect and identify fluorine-containing compounds. 19F is an important nucleus for NMR spectroscopy because of its receptivity and large chemical shift dispersion, which is greater than that for proton nuclear magnetic resonance spectroscopy. Operational details 19F has a nuclear spin (I) of and a high gyromagnetic ratio. Consequently, this isotope is highly responsive to NMR measurements. Furthermore, 19F comprises 100% of naturally occurring fluorine. The only other highly sensitive spin NMR-active nuclei that are monoisotopic (or nearly so) are 1H and 31P. Indeed, the 19F nucleus is the third most receptive NMR nucleus, after the 3H nucleus and 1H nucleus. The 19F NMR chemical shifts span a range of about 800 ppm. For ''organo''fluorine compounds the range is narrower, being about −50 to −70 ppm (for CF3 groups) to −200 to −220 pp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetramethylsilane
Tetramethylsilane (abbreviated as TMS) is the organosilicon compound with the formula Si(CH3)4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral. TMS is a building block in organometallic chemistry but also finds use in diverse niche applications. Synthesis and reactions TMS is a by-product of the production of methyl chlorosilanes, SiCl''x''(CH3)4−''x'', via the direct process of reacting methyl chloride with silicon. The more useful products of this reaction are those for ''x'' = 1 ( trimethylsilyl chloride), 2 ( dimethyldichlorosilane), and 3 ( methyltrichlorosilane). TMS undergoes deprotonation upon treatment with butyllithium to give (H3C)3SiCH2Li. The latter, trimethylsilylmethyl lithium, is a relatively common alkylating agent. In chemical vapor deposition, TMS is the precursor to silicon dioxide or silicon carbide, depending on the deposition conditions. In the formation of silicon carbide, carbosilanes, such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DSS (NMR Standard)
Sodium trimethylsilylpropanesulfonate (DSS) is the organosilicon compound with the formula (CH3)3SiCH2CH2CH2SO3−Na+. It is the sodium salt of trimethylsilylpropanesulfonic acid. A white, water-soluble solid, it is used as a chemical shift standard for proton NMR spectroscopy of aqueous solutions. The chemical shift, specifically the signal for the trimethylsilyl group, is relatively insensitive to pH. The proton spectrum of DSS also exhibits resonances at 2.91 ppm (m), 1.75 ppm (m), and 0.63 ppm (m) at an intensity of 22% of the reference resonance at 0 ppm. Alternatives Sodium trimethylsilyl propionate (TSP) is a related compound used as an NMR standard. It uses a carboxylic acid instead of the sulfonic acid In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is kn ... found in DSS t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethylsilylpropanoic Acid
Trimethylsilylpropanoic acid (TMSP or TSP) is a chemical compound containing a trimethylsilyl group. It is used as internal reference in nuclear magnetic resonance for aqueous solvents (e.g. D2O). For that use it is often deuterated (3-(trimethylsilyl)-2,2,3,3-tetradeuteropropionic acid or TMSP-''d''4). Other internal references that are frequently used in NMR experiments are DSS and tetramethylsilane Tetramethylsilane (abbreviated as TMS) is the organosilicon compound with the formula Si(CH3)4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral. TMS is a building block in organometallic chemistry but als .... References Propionic acids Trimethylsilyl compounds Nuclear magnetic resonance {{NMR-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetramethylsilane
Tetramethylsilane (abbreviated as TMS) is the organosilicon compound with the formula Si(CH3)4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral. TMS is a building block in organometallic chemistry but also finds use in diverse niche applications. Synthesis and reactions TMS is a by-product of the production of methyl chlorosilanes, SiCl''x''(CH3)4−''x'', via the direct process of reacting methyl chloride with silicon. The more useful products of this reaction are those for ''x'' = 1 ( trimethylsilyl chloride), 2 ( dimethyldichlorosilane), and 3 ( methyltrichlorosilane). TMS undergoes deprotonation upon treatment with butyllithium to give (H3C)3SiCH2Li. The latter, trimethylsilylmethyl lithium, is a relatively common alkylating agent. In chemical vapor deposition, TMS is the precursor to silicon dioxide or silicon carbide, depending on the deposition conditions. In the formation of silicon carbide, carbosilanes, such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base units is 1/s or s−1, meaning that one hertz is one per second or the reciprocal of one second. It is used only in the case of periodic events. It is named after Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. For high frequencies, the unit is commonly expressed in multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pure Appl
Pure may refer to: Computing * Pure function * PureSystems, a family of computer systems introduced by IBM in 2012 * Pure Software, a company founded in 1991 by Reed Hastings to support the Purify tool * Pure-FTPd, FTP server software * Pure (programming language), functional programming language based on term rewriting * Pure Storage, a company that makes datacenter storage solutions Companies and products * Pure (app), dating app * Pure (company), a British consumer electronics company specialising in digital radios * Pure (restaurant chain), a British fast food chain * Pure Insurance, Privilege Underwriters Reciprocal Exchange * Pure Trading, a Canadian electronic communication network operated by CNQ * Pure Oil, a U.S. chain of gas stations * Propulsion Universelle et Récuperation d'Énergie (PURE), a motorsport engineering company * Pure FM (Portsmouth), a university radio station based in Portsmouth, UK * Pure (Belgian radio station), a former Belgian radio stati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light. The interval of time between events is called the period. It is the reciprocal of the frequency. For example, if a heart beats at a frequency of 120 times per minute (2 hertz), its period is one half of a second. Special definitions of frequency are used in certain contexts, such as the angular frequency in rotational or cyclical properties, when the rate of angular progress is measured. Spatial frequency is defined for properties that vary or cccur repeatedly in geometry or space. The unit of measurement of frequency in the International System of Units (SI) is the hertz, having the symbol Hz. Definitions and units For cyclical phenomena such as oscillations, waves, or for examp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parts Per Million
In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantity, dimensionless quantities, e.g. mole fraction or mass fraction (chemistry), mass fraction. Since these fraction (mathematics), fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are * parts-per-million - ppm, * parts-per-billion - ppb, * parts-per-trillion - ppt, * parts-per-quadrillion - ppq, This notation is not part of the International System of Units - SI system and its meaning is ambiguous. Applications Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water. The quantity "1 ppm" can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta (letter)
Delta ( ; uppercase Δ, lowercase δ; , ''délta'', ) is the fourth letter of the Greek alphabet. In the system of Greek numerals, it has a value of four. It was derived from the Phoenician alphabet, Phoenician letter Dalet (letter), dalet 𐤃. Letters that come from delta include the Latin alphabet, Latin D and the Cyrillic script, Cyrillic De (Cyrillic), Д. A river delta (originally, the Nile Delta, delta of the Nile River) is named so because its shape approximates the triangular uppercase letter delta. Contrary to a popular legend, this use of the word ''delta'' was not coined by Herodotus. Pronunciation In Ancient Greek, delta represented a voiced dental plosive . In Modern Greek, it represents a voiced dental fricative , like the "''th''" in "''that''" or "''this''" (while in foreign words is instead commonly transcribed as ντ). Delta is romanization of Greek, romanized as ''d'' or ''dh''. Uppercase The uppercase letter Δ is used to denote: * Change of any changeable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
