Chemical synthetic route

The selection of a small organic molecule as the target for a chemical synthetic route may arise from any potential application for this molecule in any specific field. The selection depends on the requirements of the individual chemical project and cannot be generalized in any way. Once the target is selected, the so-called retrosynthetic... 

Rhodium-catalysed hydroboration is a powerful tool for introducing chirality into a styrene-derivative. (Figure 1.1)[2] This was in competition to the established route based on chiral resolution using separation of diastereomers formed from reaction of the racemic amines with homo-chiral acids (natural pool). However, although the process appeared favourable from the chemical synthetic route, the process was practically impossible owing to there being no supplier of catecholborane on large scale at the time. 

K. MaUick, M.J. Witcomb, A. Dinsmore, and M.S. Scurrell, Fabrication of a metal nanoparticles and polymer nanofibers composite material by in situ chemical synthetic route, Langmuir, 21, 7964-7967 (2005). 

FIGURE 6 Chemical synthetic routes of pt lythiophcnc and its derivatives [77]. 

Figure 4.1. Comparison of electrochemical and chemical synthetic routes to PHCs.

It was recently reported that PAn-CNT composite can also be made from enzymatic synthesis [84]. This is a non-conventional synthetic route (although essentially stiU a chemical synthetic route) for the making of such composites. However, as an enzymatic process, it has the merit of being environmentally friendly. Also., the PAn-CNT composites made from this method had comparable stmcture and morphology to those made of the conventional chemical oxidation method. The specific capacitance of this composite was 440 F g [84]. 

Abiotic chemical synthetic routes are being developed to convert biomass into furanic compounds such as 2-5-dimethyl furan, 5-(ethoxymethyl) furfural, and... 

Often more than one synthetic route may be available to prepare a particular com pound Indeed it is normal to find m the chemical literature that the same compound has been synthesized m a number of different ways As we proceed through the text and develop a larger inventory of functional group transformations our ability to evaluate alternative synthetic plans will increase In most cases the best synthetic plan is the one with the fewest steps... 

Some representative backbone stmctures of PQs and PPQs and their T data are given in Table 1. As in other amorphous polymers, the Ts of PQs and PPQs are controlled essentially by the chemical stmcture, molecular weight, and thermal history. Several synthetic routes have been investigated to increase the T and also to improve the processibiUty of PPQ (71). Some properties of PPQ based on 2,3-di(3,4-diaminophenyl)quinoxaline and those of l,l-dichloro-2,2-bis(3,4-diaminophenyl)ethylene are summarized in Table 2. 

Synthesis and Manufacture of Amines. The chemical and busiaess segments of amines (qv) and quaternaries are so closely linked that it is difficult to consider these separately. The majority of commercially produced amines origiaate from three amine raw materials natural fats and oils, a-olefins, and fatty alcohols. Most large commercial manufacturers of quaternary ammonium compounds are fully back-iategrated to at least one of these three sources of amines. The amines are then used to produce a wide array of commercially available quaternary ammonium compounds. Some iadividual quaternary ammonium compounds can be produced by more than one synthetic route. 

For a viable commercial process, the selection of materials and the choice of synthetic route is governed primarily by cost, not by overall yield. The selection of starting material is dictated usually by the desked C-3 substituent. For cephalosporins containing 3-acetoxymethyl or 3-(substituted)methyl such as 3-thiomethyl and 3-aminomethyl derived moieties, the most dkect synthetic route is from cephalosporin C, whereas pencillin V or G is the preferred starting material for the synthesis of the C-3 methyl cephalosporins. The three chemical transformations (2), (5), and 6) can potentially be carried out in a variety of ways, the precise sequence being determined by a balance of competing factors such as cost and optimization of yield (87). 

Chemical Synthesis. The chemical synthesis of citric acid was reported in 1880 (27). Since then, many different synthetic routes have been investigated, reported, and patented (28—36). However, none of these have proven to be commercially feasible. 

When topological strategies are used concurrently with other types of strategic guidance several benefits may result including (1) reduction of the time required to find excellent solutions (2) discovery of especially short or convergent synthetic routes (3) effective control of stereochemistry (4) orientational (regiochemical) selectivity (5) minimization of reactivity problems and (6) facilitation of crucial chemical steps. 

Many organic chemical transformations have been carried out in ionic liquids hydrogenation [4, 5], oxidation [6], epoxidation [7], and hydroformylation [8] reactions, for example. In addition to these processes, numerous synthetic routes involve a carbon-carbon (C-C) bond-forming step. As a result, many C-C bondforming procedures have been studied in ambient-temperature ionic liquids. Among those reported are the Friedel-Crafts acylation [9] and allcylation [10] reactions, allylation reactions [11, 12], the Diels-Alder reaction [13], the Heck reaction [14], and the Suzuld [15] and Trost-Tsuji coupling [16] reactions. 

Hydroformylation of nitrile rubber is another chemical modification that can incorporate a reactive aldehyde group into the diene part and further open up new synthetic routes to the formation of novel nitrile elastomers with a saturated backbone containing carboxyl or hydroxyl functionalities. 

Isoprene is the second important conjugated diene for synthetic rubber production. The main source for isoprene is the dehydrogenation of C5 olefins (tertiary amylenes) obtained by the extraction of a C5 fraction from catalytic cracking units. It can also be produced through several synthetic routes using reactive chemicals such as isobutene, formaldehyde, and propene (Chapter 3). 

The synthesis of porphyrins from monopyrrolic, dipyrrolic, tripyrrolic and tctrapyrrolic precursors requires, even for an experienced porphyrin chemist, a substantial amount of time and effort to accomplish. As an alternative to these total synthetic routes, nature provides a source of prefabricated porphyrins. Among the several porphyrins which can be isolated from natural material,s the red blood pigment heme, protoporphyrin dimethyl ester81 b and hemato-porphyrin, both derived from heme, are the only compounds which can be obtained in sufficient amounts. Heme is available in almost unlimited amounts from slaughter-house waste. From 1 L of blood ca. 1 g of heme can be isolated.81 b Currently, heme is offered commercially by chemical retailers at a relatively low price so that is cheaper to buy hemin than to perform a self-isolation in the laboratory. 

---