Hydrogen-type spectra

Hydrogenation at 373 K again led to propane and a very weak spectrum on evacuation (248). In this case, however, readmission of H2 at 473 K. led to a more substantial CH2-rich alkyl-type spectrum that was completely removed by... 

Figure 10.1 -NMR spectrum of thioredoxin, reducedform. Labels show chemical-shift values typical of various hydrogen types in protein chains having random coil conformation. Some signals lie outside these ranges because of specific interactions not present in random coils. Atom labels are as found in PDB coordinate files. Spectrum generously provided by Professor John M. Louis.

The area under an NMR peak can be determined by integration. Comparison of the integration (areas) of the signals on an NMR spectrum gives the ratio of hydrogen types in a molecule if the molecular formula is known, the actual number of each type of hydrogen can be determined. 

This is called the fine structure of the spectral lines. Its theory was given by Sommerfeld for the case of atoms of the hydrogen type (H, He+, Li++), and was tested by Fowler and Paschen on the spectrum of singly ionized helium (He+), which was found in complete agreement with the theory. The test is easier wdth He+ than with H for this reason, that the eiu. rgy terms of He+ are four times as far apart, on account of the nuclear charge number Z being doubled, w hereas the... 

Fundamental to the use of NMR is the ready correlation of measurable spectrum quantities with the structure of a molecule xmder study. Consider the simple molecule ethanol. Ethanol has three bands in its hydrogen NMR spectrum that correlate with the three distinct types of hydrogen atoms present in the molecule. The area ratio of the three bands is 1 2 3 and this reflects the number ratio of the hydrogen atoms seen in the structure of... 

Draw a Grotrian-type diagram for the first four lines of the Lyman series in the hydrogen atom spectrum. Be sure to include all allowed transitions. 

In straight-run petroleum products which do not usually contain olefins, four types of hydrogen can be easily differentiated as seen in the spectrum in Figure 3.10 ... 

The tautomeric behavior of compounds of type 59 has been discussed by Meyer and Vaughan. An intramolecularly hydrogen-bonded 0X0 structure has been assigned to 60 on the basis of its infrared spectrum," whereas unambiguous chemical evidence, i.e., ozo-nolysis to succimide, confirmed the isolation of 61 in the oxo form. The foregoing results may be summarized as follows potential a-hydroxypyrroles exist as pyrrolones. Substituents in the 3-position and in the 5-position favor the A and the A -pyrrolone structure, respectively, as is to be expected. For 3,4,5-trisubstituted compounds, such as 61b, the A -sti ucturc appears to be preferred. An electron-... 

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