Nitrogen atomic weights

Figure 10.3-40. The rating for the disconnection strategy carbon-heteroatom bonds is illustrated, Please focus on the nitrogen atom of the tertiary amino group. It is surrounded by three strategic bonds with different values. The low value of 9 for one ofthese bonds arises because this bond leads to a chiral center. Since its formation requires a stereospecific reaction the strategic weight of this bond has been devalued. In contrast to that, the value of the bond connecting the exocyclic rest has been increased to 85, which may be compared with its basic value as an amine bond.

First the peak for the molecular ion M for all compounds that contain only car bon hydrogen and oxygen has an m z value that is an even number The presence of a nitrogen atom m the molecule requires that the m z value for the molecular ion be odd An odd number of nitrogens corresponds to an odd value of the molecular weight an even number of nitrogens corresponds to an even molecular weight... 

When the nominal molecular weight of a compound containing only C, H, O, and N is odd, the number of nitrogen atoms must be odd. 

Annular nitrogen atoms can form hydrogen bonds, and if the azole contains an NH group, association occurs. Imidazole (84) shows a cryoscopic molecular weight in benzene 20 times that expected. Its boiling point is 256 °C, which is higher than that of 1-methyl-imidazole (198 °C). 

Nitrogen has two stable isotopes N (relative atomic mass 14.003 07, abundance 99.634%) and (15.000 11, 0.366%) their relative abundance (272 1) is almost invariant in terrestrial sources and corresponds to an atomic weight of 14.00674(7). Both isotopes have a nuclear spin and can be used in nmr experiments. though... 

An important group of antimetabolites are the aza analogs of pyrimidine and purine bases which are theoretically derived by a replacement of the methine group of a pyrimidine or purine nucleus with a nitrogen atom. This replacement represents a relatively minor alteration of the structure of these substances as it does not change the functional groups, practically preserves the molecular weight, and produces almost isosteric compounds. The replacement of the methine... 

The nitrogen rule of mass spectrometry says that a compound with an odd number of nitrogen atoms has an odd-numbered molecular weight. Thus, the presence of nitrogen in a molecule is detected simply by observing its mass spectrum. An odd-numbered molecular ion usually means that the unknown... 

Nitrogen rule (Section 24.10) A compound with an odd number of nitrogen atoms has an odd-numbered molecular weight. 

Unsurprisingly, Mendeleev (1895, p. 543) himself was more committed Rayleigh and Ramsay s gas had to fit in the table somehow, and an atomic weight of 40 meant it did not fit—his favoured hypothesis was that the gas consists of tri-atomic nitrogen, N3, with the hypothesis of an hexatomic element the runner-up. 

The positive-ion Cl spectrum, using ammonia as a reagent gas, of an analyte containing carbon, hydrogen, oxygen and two nitrogen atoms, has a molecular species at m/z 222. What is the molecular weight of the compound Involved ... 

This is either an (M + 1)+ or an (M - -18)+ ion, depending upon the relative proton affinities of the analyte and ammonia. The molecular weight is therefore either 221 or 204 Da. Since the molecule contains an even number of nitrogen atoms, it must have an even molecular weight. The molecular species must therefore be (M - -18)+ and so the molecular weight is 204 Da. 

Organic polymers claimed to be effective swelling clay and mineral fine particle stabilizers in the patent literature can be divided into four classes. The polymers of class 1 have the quaternary nitrogen atom as part of the polymer backbone (6-10). Polymers in this class include poly(dimethylamine-co-epichlorohy-drin, abbreviated poly(DMA-co-EPl), and poly(N,N,N, N,-tetramethyl-l,4-l,4-diaminobutane-co-l,4-dichlorobutane), abbreviated poly (TMDAB-co- DCB). These low molecular weights are not surprising since these are condensation polymers. Molecular weights cited range from 800 to 800,000 daltons. 

The third class of polymers contains one or more nitrogen atoms on a pendant sidechain in the polymer repeat unit (13,14). The nitrogen may or may not be quaternary. In addition to being swelling clay stabilizers, these polymers also stabilize nonswelling mineral fine particles. Limited molecular weight data ig available but molecular weight values from 50,000 to 1 X 10 daltons have been cited for various polymers. 

Results indicate that the effectiveness of quaternary ammonium salt polymers in stabilizing swelling clays and mineral fine particles is dependent on monomer chemical structure and polymer molecular weight. Long flexible pendant sidechains containing quaternary nitrogen atoms appear to be required for these polymers to function as mineral fine particle stabilizers. 

Every element has an atomic weight approximately (but not exactly) equal to the total number of protons and neutrons that are present in each of its atoms. The atomic weights are not exactly equal to this sum because, in addition to other reasons, not all atoms of a particular element have the same number of neutrons. Most elements have one or more isotopes, which means atoms with the same number of protons but different numbers of neutrons. For example, the element nitrogen has two natural isotopes, 14N which has 7 protons and 7 neutrons, and 15N which has 7... 

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