Structure general organization

Karfunkel H R and R J Gdanitz 1992. Ah initio Prediction of Possible Crystal Structures for General Organic Molecules. Journal of Computational Chemistry 13 1171-1183. 

Before the advent of NMR spectroscopy infrared (IR) spectroscopy was the mstrumen tal method most often applied to determine the structure of organic compounds Although NMR spectroscopy m general tells us more about the structure of an unknown com pound IR still retains an important place m the chemist s inventory of spectroscopic methods because of its usefulness m identifying the presence of certain functional groups within a molecule... 

For even more convenience in representing the structures of organic compounds, particularly in printed material, line formulas are used, so-called because they are printed on one line. In line formulas, each carbon atom is written on a line adjacent to the symbols for the other elements to which it is bonded. Line formulas show the general sequence in which the carbon atoms are attached, but in order to interpret them properly, the permitted total bond orders of all the respective atoms must be kept in mind. Again referring to the compounds (a) to (e) described above, the line formulas are as follows ... 

For many years, investigations on the electronic structure of organic radical cations in general, and of polyenes in particular, were dominated by PE spectroscopy which represented by far the most copious source of data on this subject. Consequently, attention was focussed mainly on those excited states of radical ions which can be formed by direct photoionization. However, promotion of electrons into virtual MOs of radical cations is also possible, but as the corresponding excited states cannot be attained by a one-photon process from the neutral molecule they do not manifest themselves in PE spectra. On the other hand, they can be reached by electronic excitation of the radical cations, provided that the corresponding transitions are allowed by electric-dipole selection rules. As will be shown in Section III.C, the description of such states requires an extension of the simple models used in Section n, but before going into this, we would like to discuss them in a qualitative way and give a brief account of experimental techniques used to study them. 

Figure 11.11 The resonance structure of a generalized organic acid RCOO-, where R is any organic group and -COO- is the acid radical, (a) shows two possible equivalent forms for this structure, and (b) the resonance structure, which is a mixture of the two.

The resonance structure of a generalized organic acid RCOO- 263... 

Marine chemists have had limited success in characterizing the molecular structure of organic matter, particularly for the dissolved compounds. Chemical analysis usually starts with the isolation of POM from DOM using a filter with a 0.2-p,m pore size. This is generally followed by elemental analysis. More sophisticated approaches involve structural analysis, but this is usually limited to detection of functional groups or broad classes of compounds. 

Dagley, S. Microbial degradation of stable chemical structures general features of metabolic pathways, in Degradation of Synthetic Organic Molecules in the Biosphere Natural Pestlcldal, and Various Other Man-Made Compounds (Washington, DC National Academy of Sciences. 1972), pp. 1-16. 

It is now known that dark- and photoconductivity is connected with the structure of organic compounds 10>. The conductivity of organic dyes and other organic compounds, like that of inorganic semiconductors, is attributable to electronic charge carriers, i.e. electrons and positive holes. The dark conductivity [Pg.87]

Electron microscopy reveals several types of protein filaments crisscrossing the eukaryotic cell, forming an interlocking three-dimensional meshwork, the cytoskeleton. There are three general types of cytoplasmic filaments— actin filaments, microtubules, and intermediate filaments (Fig. 1-9)—differing in width (from about 6 to 22 nm), composition, and specific function. All types provide structure and organization to the cytoplasm and shape to the cell. Actin filaments and microtubules also help to produce the motion of organelles or of the whole cell. 

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