Atom utilization

The various methods that are used for the production of aromatic acids from the corresponding substituted toluenes are outlined in Figure 1. The first two methods -chlorination/hydrolysis and nitric acid oxidation - have the disadvantage of relatively low atom utilization (ref. 13) with the concomitant inorganic salt production. Catalytic autoxidation, in contrast, has an atom utilization of 87% (for Ar=Ph) and produces no inorganic salts and no chlorinated or nitrated byproducts. It consumes only the cheap raw material, oxygen, and produces water as the only byproduct. 

Certainly, this is a green chemical reaction with a 100% atom utility, which recovers the waste NO and O2 to produce a valuable fertilizer with the help of ammonia. 

Sheldon, R.A. (2000) Atom Utilization, E Factors and the Catalytic Solution. C.R. Acad. Sci. Paris, Serie, lie, Chimie/Chemistry, 3, 541-551. 

However, one category of selectivity is largely ignored by organic chemists the atom selectivity , or what is variously called atom economy (Trost, 1991, 1995), atom efficiency, or atom utilization solvents (Sheldon, 1992, 1992a, 1993, 1994, 1996, 1997, 1997a). The complete disregard of this parameter is the root cause of the waste problem in fine chemicals manufacture. 

The atom utilization or atom efficiency concept is a useful tool for rapid evaluation of the amount of waste that will be generated by alternative routes to a particular product. It is calculated by dividing the molecular weight of the desired product by the sum total of the molecular weights of all the substances produced in the stoichiometric equation of the reaction(s) in question. The comparison is made on a theoretical (i.e. 100% chemical yield) basis. Fig. 2.8 shows a simple illu.stration of the concept for ethylene oxide manufacture. 

Covalent bonding is the sharing of one or more pairs of electrons by two atoms. The covalent bonds in a molecule a covalently bonded compound are represented by a dash. Each dash is a shared pair of electrons. These covalent bonds may be single bonds, one pair of shared electrons as in H-H double bonds, two shared pairs of electrons as in H2C=CH2 or triple bonds, three shared pairs of electrons, N=N . It is the same driving force to form a covalent bond as an ionic bond—completion of the atom s octet. In the case of the covalent bond, the sharing of electrons leads to both atom utilizing the electrons towards their octet. 

The graphite furnace method of atomization utilizes a small graphite tube furnace to electrically heat rapidly a small volume of the analyte solution contained inside to a temperature that eventually causes atomization. 

In the same way, the biphasic carbonylation of benzyl alcohol (Figure 9.7) was achieved.Phenylacetic acid was obtained in 11% yield, 100% selectivity, and 100% atom utilization. 

Similarly, acylamino acids can be prepared with 100% atom utilization via palladium-catalyzed amidocarbonylation. " The method was used for the synthesis of a surfactant from sarcosine (Figure 9.8). 

One of the major themes in the Brundtland Report was a concept now known in green chemistry as atom economy (also sometimes known as atom utilization), the notion that chemical manufacturing should attempt to conserve as much of the raw materials (and, hence, atoms) with which it begins as possible and to prevent losing materials (and, hence, atoms) to the environment during manufacturing processes. 

REAGENT FORMULA WEIGHT ATOMS UTILIZED WEIGHT OF ATOMS UTILIZED ATOMS NOT UTILIZED WEIGHT OF ATOMS NOT UTILIZED... 

While evaporative methods of generating C atoms utilize bulk carbon and a great deal of thermal or photochemical energy, another approach is to use the exother-micity of the decomposition of a suitable precursor to produce C atoms. These methods yield what are called chemically generated carbon atoms and will be outlined below. 

The procedure presented for the dehydrogenation of secondary alcohols is very easy to reproduce and high atom utilization achieved presents a major benefit over hydrogen-transfer oxidations. Results for the dehydrogenation of various substrates using Ru(OCOCF3)2(CO)(PPh3)2 as a catalyst are presented in Table 5.2. 

As noted above, a knowledge of the stoichiometric equation allows one to predict the theoretical minimum amount of waste that can be expected. This led to the concept of atom economy [8] or atom utilization [9] to quickly assess the environmental acceptabihty of alternatives to a particular product before any experiment is performed. It is a theoretical number, that is, it assumes a chemical yield of 100% and exactly stoichiometric amounts and disregards substances which do not appear in the stoichiometric equation. 

Bismuth is the fifth member of the nitrogen family of elements and, like its congeners, possesses five electrons in its outermost shell, 6s 6p. In many compounds, the bismuth atom utilizes only the three 6p electrons in bond formation and retains the two 6x electrons as an inert pair. Compounds are also known where bismuth is bonded to four, five, or six other atoms. Many bismuth compounds do not have simple molecular structures and exist in the solid state as polymeric chains or sheets. 

The novel BHC ibuprofen process with its three catalytic steps and 80% atom utilization (99% with recycle) replaces a process with six stoichiometric steps at < 40% atom utilization. 

The BHC ibuprofen process is an innovative, efficient technology that revolutionized bulk pharmaceutical manufacturing. The new technology with its three catalytic steps achieves approximately 80% atom utilization, which is increased to almost 99% if recovery of the by-product acetic acid is included. It replaces a pro-... 

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