Features of molecular structure

Explosive Power vs Oxygen Balance, Correlation of. The relationship of oxygen balance to expl power as measured by ballistic mottathas been studied empirically. Starting from modified oxygen, balance developed for detonation velocity calculations, a numerical measure called the power index is derived which correlates closely the features of molecular structure with.the power values. Expl power has also been expressed as an additive function of details of molecular structure. This is the basis for a method whereby power values may be derived which agree with experimental results to about... 

The foregoing pages have shown a number of ways in which physical constants vary with molecular structure. Petroleum chemists and automotive engineers have come to recognize that the performance of a motor fuel in an internal combustion engine is also dependent upon the structure of the hydrocarbon molecules which the fuel contains. This does not mean that engine performance is a function of the physical constants, but rather that the features of molecular structure which determine the one also determine the other. 

The observation of the colour and the degree of absorption associated with each index is of obvious value for identification purposes the larger the number of characteristics observed, the more certain the identification. Observations of pleochroism may also be useful as indications of certain features of molecular structure. (See Chapter VIII.)... 

One either has to reject the use of dot formulas in representing important features of molecular structure or one may-attempt to change their meaning so that the observed equivalence of oxygen atoms in nitrate ion still can be described. In view of the otherwise great utility of the dot representation, the latter course is often followed. 

This is referred to as the 2-level model (6) and was used in the past to understand trends in p with structural modifications of the molecule. With the computational methods and experimental accuracy available today this method is viewed as inadequate although it does serve to illustrate the essential features of molecular structure that control p. In the two level model, px (the component of the tensor along the charge transfer axis) is given by... 

This article is not the place in which to consider statistical methods in detail, but the use of GRID maps to interpret interesting features of molecular structures will now be described. 

As the number of connections is sensitive to different features of molecular structure such as size, branching, cyclicity and multiple bonds it was used by Bertz to define its -> molecular complexity index. 

It is tempting to suppose that the whole of this elaborate graphical and spatially expressed calculus is a merely formal accounting scheme with no direct ontological content. It is a successful scheme in aceounting for most of the features of molecular structures and many of the features of ehemical reactions. It has often been used in making predictions and deductions about such of these features as are directly measurable for comparison. But for all of its empirical success, it may be only a formal scheme. 

It is always tempting for the chemist to interpret observations on SARs in mechanistic terms and to postulate means by which the biological activity could be brought about through some feature of molecular structure or chemical activity which seems significant in the... 

Chemical graph theory has been the basis for new applications in structure-property methods during recent years. With an emphasis on the molecular skeleton, numerical indexes have been developed that represent features of molecular structure. These indexes are numerical values that parallel variation... 

Topological indexes should be based on the most significant features of molecular structure, including atom identity, bonding environment of each atom, and the existence of hydrogen atoms bonded to the skeletal atom. Each of these aspects is distinctly electronic in nature. 

The major concern is that of skin sensitisation. When a material comes in contact with the skin, it may react with a protein present in the skin to form a modified protein and this could become an antigen as far as the immune system is concerned. If this happens, the immune system will produce antibodies to combat the antigen. If the immune system over-reacts, an allergic reaction will result and a rash will break out on the skin. Thus, skin sensitisers do not produce a reaction on the first contact with the skin, but only after repeated exposure. Fortunately, we now know the basic features of molecular structure which are associated with skin sensitisation and can design molecules which will not behave in this way. This is a good example of the importance of safety SARs to the discovery chemist. Of course, predictions are not the ultimate test and therefore many companies, especially in the pharmaceutical industry, invest considerable amount in the development of rapid in vitro screens to detect any adverse toxicological effects. 

The results obtained from the measurement of the observed angle of rotation, ttobs/ are generally expressed in terms of specific rotation [a].The sign and magnitude of [a] are dependent on the specific molecule and are determined by complex features of molecular structure and conformation they cannot be easily explained or predicted. The specific rotation is a physical constant characteristic of a substance. The relationship of [a] to aobs is as follows ... 

The parameters of molecular structure of p-chlorobenzenesulfonamido-/3-thioIactone are shown on Figures 1 and 2 [14]. It is evident from Figure 1 that an important feature of molecular structure is the existance of strong intermolecular hydrogen bonding between —NH--------------OC— groups with a bond distance of 2.83 A. Furthermore it was... 

In Section 1.4, we represented the electronic structures of molecules as Lewis structures, which enable us to explain the connectivity of atoms in a molecule. This is the most fundamental feature of molecular structure. We then used valence-shell electron-pair repulsion (VSEPR) theory to explain molecular geometry. 

---