Selected Nitrogen and Sulfur Compounds

As is true of amines, nitrogen-bearing compounds such as amides, nitriles, and nitro compounds must follow the Nitrogen Rule (explained more completely in Section 8.4) If they contain an odd number of nitrogen atoms, they must have an odd-numbered molecular weight. 

The mass spectra of amides usually show observable molecular ion peaks. The fragmentation patterns of amides are quite similar to those of the corresponding esters and acids. The presence of a strong fragment ion peak at mie = 44 is usually indicative of a primary amide. This peak arises from ct-cleavage of the following sort. 

Ahphatic nitriles usually undergo fragmentation so readily that the molecular ion peak is too weak to be observed. However, most nitriles form a peak due to the loss of one hydrogen atom, producing an ion of the type R-CH=C=N. Although this peak may be weak, it is a useful diagnostic peak in characterizing nitriles. In the mass spectrum of hexanenitrile (Fig. 8.43), this peak appears at mie = 96. 

When the alkyl group attached to the nitrile functional group is a propyl group or some longer hydrocarbon group, the most intense peak in the mass spectrum results from a McLafferty rearrangement  

This peak, which appears in the mass spectrum of hexanenitrile, can be quite useful in characterizing an aliphatic nitrile. Unfortunately, as the alkyl group of a nitrile becomes longer, the probability of formation of the ion, which also appears at mie =Xl, increases. With high-molecular- 

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VIII. Atmospheric Reactions of Selected Nitrogen and Sulfur Compounds... 

The Bureau of Mines together with the American Petroleum Institute made concentrated efforts to study both nitrogen and sulfur compounds in domestic crudes in the 1950-1964 period (2,3,4,5). The sulfur studies (API Report of Project 48), while limited to low-molecular-weight compounds, were the first comprehensive attempt to integrate liquid-solid and gas-liquid chromatography with selective chemical desulfurizations and mass spectrometry more than 100 individual sulfur compounds were... 

The aromatic compounds are the derivatives of phenylpropane, which are aldehydes, alcohols, phenols, methoxy, and methylenedioxy in nature. A few nitrogen and sulfur compounds present in essential oils are also characterized as plant essential constituents. A list of selected and important antimicrobial components of essential oils has been presented in Fig. 132.1. 

Matsumoto and coworkers have begin to explored the aprplication of SILMs for the selective permeation of organosulfur and nitrogenated compounds. They preliminary studies had demonstrated that SILMs has a good potential for the separation process of organic nitrogen and sulfur compounds from the fuels (Matsumoto et al., 2006 and 2007). 

A flow diagram for the system is shown in Figure 5. Feed gas is dried, and ammonia and sulfur compounds are removed to prevent the irreversible buildup of insoluble salts in the system. Water and soHds formed by trace ammonia and sulfur compounds are removed in the solvent maintenance section (96). The pretreated carbon monoxide feed gas enters the absorber where it is selectively absorbed by a countercurrent flow of solvent to form a carbon monoxide complex with the active copper salt. The carbon monoxide-rich solution flows from the bottom of the absorber to a flash vessel where physically absorbed gas species such as hydrogen, nitrogen, and methane are removed. The solution is then sent to the stripper where the carbon monoxide is released from the complex by heating and pressure reduction to about 0.15 MPa (1.5 atm). The solvent is stripped of residual carbon monoxide, heat-exchanged with the stripper feed, and pumped to the top of the absorber to complete the cycle. 

Summary of selected physical-chemical properties of nitrogen and sulfur containing compounds at 25°C. 

Processes are of two types, catalytic and tbcnnaL However, apart from the operadng condidons, their flow sheets are identicaL Depending on the feedstock, a simplihed version is available with dealkylation alone, and another more-elaborate version, which includes pretreatment of the pyrolysis cut intended to convert the diolehns, stable sulfur compounds, nitrogen and oxygen compounds, etc. by selective hydrogenadon. 

Since there are many drugs and environmental pollutants that contain sulfur, it is of considerable interest that FMO preferentially catalyzes the oxidation of sulfur in compounds containing both nitrogen and sulfur. Thus, FMO is an important enzyme system for the oxidation of selected classes of xenobiotics, and its spectrum complements that of the P450 system because the latter prefers oxidation of carbon atoms. Other ways in which FMO enzymes differ from many microsomal P450 isozymes include their... 

Because coal-derived liquids and tars are usually complex mixtures of organic chemicals, the separation and identification of individual PACs in these samples have been best accomplished by using open-tubular-column (capillary-column) gas chromatography (GC) (3, 4). Selective detectors for nitrogen and sulfur, as well as mass spectrometry (MS), can be easily combined with GC. Especially when authentic standard reference compounds and selective stationary phases (5-10) are used, capillary-column GC is, by far, the easiest and most reliable technique available. 

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