Chemical derivation

Chemical derivation is frequently used to analyze by gas chromatography molecules of low volatility because they are too polar. Exchangeable hydrogen atoms (in particular 

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There are ill-defined limits on EI/CI usage, based mostly on these issues of volatility and thermal stability. Sometimes these limits can be extended by preparation of a suitable chemical derivative. For example, polar carboxylic acids generally give either no or only a poor yield of molecular ions, but their conversion into methyl esters affords less polar, more volatile materials that can be examined easily by EL In the absence of an alternative method of ionization, EI/CI can still be used with clever manipulation of chemical derivatization techniques. 

Many different processes using HF as a reactant or source of fluorine are employed in the manufacture of fluorinated chemical derivatives. In many cases the chemistry employed is complex and in some cases proprietary. Electrochemical fluorination techniques and gaseous fluorine derived from HF are used in some of these appHcations. 

Some of the chemical derivatives, especially those tied to agricultural uses, tend to experience some cycHcal demand. However, because of the speciali2ed nature of many of the fluorinated chemicals, these products are positioned in strong, high performance market areas having above average growth rates. 

In addition to chemical derivatives, purity of hGH must also be established with respect to physically associated forms. The hydrophobically linked, noncovalent dimer of hGH found to exhibit relatively low biological activity (21) is present at a level of 1—2% ia most hGH preparations at the time of... 

Apart from lactic and hydroxyacetic acids, other a- and P-hydroxy acids have been small-volume specialty products produced in a variety of methods for specialized uses. y-Butyrolactone [96 8-0] which is the monomeric inner ester of y-hydroxybutyric acid [591-81-17, is a large-volume chemical derived from 1,4-butanediol (see Acetylene-derived chemicals). 

Maleic hydra2ide [123-33-1] (10) is one of a number of commercial agricultural chemicals derived from maleic anhydride. Maleic hydra2ide was first prepared ia 1895 (39) but about 60 years elapsed before the iatermediate products were elucidated (40). 

Oxahc acid is used in various industrial areas, such as textile manufacture and processing, metal surface treatments (qv), leather tanning, cobalt production, and separation and recovery of rare-earth elements. Substantial quantities of oxahc acid are also consumed in the production of agrochemicals, pharmaceuticals, and other chemical derivatives. 

Ced rwood. Many varieties of cedarwood oil are obtained from different parts of the world. They are produced mainly by steam distillation of chipped heartwood, but some are also produced by solvent extraction. The oils, which vary significantly ia chemical composition, are used ia perfumes as such, but the main uses are as distillation fractions and chemical derivatives. For the latter purposes the most used oils, which are similar ia composition, are from Texas ia the United States (Juniperus mexicand) and from China Cupressusfunebris). The principal constituents of these oils are cedrene [11028-42-5] (4), thujopsene [470-40-6] (5), and cedrol [77-53-2] (6). The first two of these are obtained together by distillation and used mostiy ia the form of acetylated derivatives. Cedrol is used as such and, to a greater extent, as its acetate ester. 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

The uses of propylene may be loosely categorized as refinery or chemical purpose. In the refinery, propylene occurs in varying concentrations in fuel-gas streams. As a refinery feedstock, propylene is alkylated by isobutane or dimerized to produce polymer gasoHne for gasoHne blending. Commercial chemical derivatives include polypropylene, acrylonitrile, propylene oxide, isopropyl alcohol, and others. In 1992, ca 64% of U.S. propylene suppHes were consumed in the production of chemicals (74). Polypropylene has been the largest consumer of propylene since the early 1970s and is likely to dominate propylene utilization for some time. 

Manufactured fibers produced from natural organic polymers are either regenerated or derivative. A regenerated fiber is one which is formed when a natural polymer or its chemical derivative is dissolved and extmded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber-formation process. A derivative fiber is one which is formed when a chemical derivative of the natural polymer is prepared, dissolved, and extmded as a continuous filament, and the chemical nature of the derivative is retained after the fiber-formation process. 

Wood is the raw material of the naval stores iadustry (77). Naval stores, so named because of their importance to the wooden ships of past centuries, consist of rosin (diterpene resin acids), turpentine (monoterpene hydrocarbons), and associated chemicals derived from pine (see Terpenoids). These were obtained by wounding the tree to yield pine gum, but the high labor costs have substantially reduced this production in the United States. Another source of rosin and turpentine is through extraction of old pine stumps, but this is a nonrenewable resource and this iadustry is in decline. The most important source of naval stores is spent sulfate pulpiag Hquors from kraft pulpiag of pine. In 1995, U.S. production of rosin from all sources was estimated at under 300,000 metric tons and of turpentine at 70,000 metric tons. Distillation of tall oil provides, in addition to rosin, nearly 128,000 metric tons of tall oil fatty acids annually (78). 

Chemicals. Although the amount of butylenes produced ia the United States is roughly equal to the amounts of ethylene and propylene produced, the amount consumed for chemical use is considerably less. Thus, as shown ia Table 10, the utilisation of either ethylene or propylene for each of at least five principal chemical derivatives is about the same or greater than the utilisa tion of butenes for butadiene, their main use. This production is only about one-third of the total the two-thirds is derived directiy from butane. The undedyiag reasons are poorer price—performance compared to derivatives of ethylene and propylene and the lack of appHcations of butylene derivatives. Some of the products are more easily derived from 1-, 2-, and 3-carbon atom species, eg, butanol, 1,4-butanediol, and isobutyl alcohol (see Acetylene-DERIVED chemicals Butyl alcohols). 

Sulfation. Sulfated castor oil, also known as turkey-red oil, represents one of the earliest chemical derivatives of castor oil. The traditional method of preparing turkey-red oil is to add concentrated sulfuric acid at a controlled rate to castor oil over a period of several hours with constant cooling and agitation of the reaction mass to maintain a temperature of 25—30°C. After acid addition is complete, the reaction mass is washed then neutralized using an alkaU solution or an amine. 

Non-elastomeric chemical derivatives of natural rubber are discussed in Chapter 30 in which chemically related naturally occurring materials such as gutta percha and balata are briefly considered. 

Whilst by far the bulk of polyamide materials are used in the form of fibres, they have also become of some importance as speciality thermoplastics of particular use in engineering applications. The fibre-forming polyamides and their immediate chemical derivatives and copolymers are often referred to as nylons. There are also available polyamides of more complex composition which are not fibre-forming and are structurally quite different. These are not normally considered as nylons (see Section 18.10). 

These materials are also often referred to as glass-clear nylons, which is different from the normal usage of the term nylon for fibre-forming polyamides and their immediate chemical derivatives. 

Many other polymers compete with cellophane such as polyethylene which is extruded as a tough film or in greater thickness as a nonbreakable bottles. Vinyl products used in films are polystyrene, polyesters, and nylon. A chemical derivative from nature rubber, chlorinated rubber, gives films of extraordinary stretch ability. 

WHO (1994). Environmental Health Criteria, 170. Assessing human health risks of chemicals derivation of guidance values for health-based exposure limits. World Health Organization, Cieneva. 

Poly(malic acid) is of pharmaceutical interest because its chemical derivatives may harbor both tissue-specific homing molecules and therapeutic effectors to be used for tissue (tumor) targeting in chemotherapy [2]. Because of its efficient production by fermentation, its biodegradability and nontoxicity, it is also considered as raw material in the industrial production of detergents, glues, and plastic materials. 

The chemistry for producing the various chemicals from benzene is discussed in this section. Figure 10-1 shows the important chemicals derived from benzene. 

Important chemicals derived from phenol are salicylic acid acetylsali-cyclic acid (aspirin) 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-triphenoxy acetic acid (2,4,5-T), which are selective herbicides and pentachlorophenol, a wood preservative ... 

Currently, the major route to maleic anhydride, especially for the newly-erected processes, is the oxidation of hutane (Chapter 6). Maleic anhydride also comes from oxidation of n-hutenes. Properties and chemicals derived from maleic anhydride are noted in Chapter 9. 

Chapter 5 discusses chemicals derived directly or indirectly from methane. Because synthesis gas is the main intermediate from methane. 

A compartment is an anatomical space in the body into which a diug or metabolite, or a chemical derivative or metabolite formed from the parent diug may distribute. 

The nitrogen mustards are cytotoxic chemotherapy agents which are chemically derived from mustard gas. Although their current use is medicinal, the predecessor of these compounds was also used for chemical warfare putposes. 

A class of chemicals derived from ammonia employed to treat steam and condensate. 

Today we face a different challenge. Environmental pressure is pushing away from S)mthetic or petro-chemically derived products, while economic factors are pulling back from often more expensive "green" options. This paradox is what fuels research into materials and products whose properties fulfill environmental and economic requirements. 

Commercial plastics polymerisation is akin to making pig s ears out of silk purses, albeit usually useful porcine ears from very worn out handbags. What were once valuable polymers are turned into generally less valuable monomers. The regenerated monomers and small chemicals from polymerisation of post-consumer plastics have no particular moral authority or intrinsic grace compared to chemicals derived from non-recycling sources. To be successful, commercial polymerisation must make economic sense in ways that are understood by those who invest dear money into capital assets. 

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