Formulas, chemical, meaning

In 1929 Carothers proposed a generally useful differentiation between two broad classes of polymers condensation polymers in which the molecular formula of the structural unit (or units) lacks certain atoms present in the monomer from which it is formed, or to which it may be degraded by chemical means, and addition polymers, in which the molecular formula of the structural unit (or units) is identical with that of the monomer from which the polymer is derived. Condensation polymers may be formed from monomers bearing two or more reactive groups of such a character that they may condense intermolecu-larly with the elimination of a by-product, often water. The polyamides and polyesters referred to above afford prime examples of condensation polymers. The formation of a polyester from a suitable hydroxy acid takes place as follows ... 

With the availability of modern experimental techniques, the structure of a compound can be established unequivocally. However, more than 100 years ago only chemical means were available for structure elucidation. The fact that only two isomers could be isolated was a good indication that a complex having the formula MX4Y2 has an octahedral structure. The argument could be made that the synthetic chemist was not able to prepare a third possible isomer or that it exists but was so unstable that it could not be isolated. 

The word nomenclature simply means naming. You have already seen some chemical formulas such as NaCl, H20, and H2S04. There are many times when having names for chemicals is more convenient than having their formulas. Chemical naming falls into two main groups that for ionic compounds formed of positive and negative ions, and that for nonionic compounds. 

A classic procedure in the chemical study of alkaloids includes extraction from a plant or animal source, chemical isolation and purification of the active principal, elucidation of the molecular formula by means of chemical degradation, mass spectrometry, infrared, ultraviolet, and nuclear magnetic resonance analyses, and laboratory synthesis of the product. Serious diffi-... 

The active substances are not used as neat chemicals. They are sold as formulated products. Products for small-scale use in house or garden are often ready-to-use formulas. That means they come in diluted form, often in spray cans, and can be used as they are. For large-scale use this is not economical, because a large part of the spray mix is simply water, needed to dilute the active substance. Therefore, pesticide products for use in agriculture or vector control are concentrates. They are diluted with water... 

A molecule is often represented by a picture or a niodel—sometimes by several pictures or several models. The atomic nuclei are represented by letters or wooden balls, and the electrons that join them by lines or dots or wooden pegs. These crude pictures and models are useful to us only if we understand what they are intended to mean. Interpreted in terms of the structural theory, they tell us a good deal about the compound whose molecules they represent how to go about making it what physical properties to expect of it—melting point, boiling point, specific gravity, the kind of solvents the compound will dissolve in, even whether it will be colored or not what kind of chemical behavior to expect—the kind of reagents the compound will react with and the kind of products that will be formed, whether it will react rapidly or slowly. We would know all this about a compound that we had never encountered before, simply on the basis of its structural formula and what we understand its structural formula to mean. 

Describe the reasoning that permits chemical formulas to be determined by purely chemical means (Section 1.3, Problems 7-10). 

Carbothialdine" i.e. 4,6-dimethylperhydro-l,3,5-thiadiazine-2-thione, the reaction product of acetaldehyde with ammonia and carbon disulfide, has been known a long time (260, 288). Various structures have been proposed for it (83, 143, 164, 234). It was also known that this product may be obtained from acetaldehyde and ammonium dithiocarbamate and that two moles of aldehyde are necessary for the reaction. The reaction products of other aldehydes and amines had also been investigated with a view to elucidating their structure (31, 108). However, Ainley and co-workers (1) in 1944 were the first to determine the structure with certainty. The instability of "carbothialdines made it difficult to determine their structure by chemical means. It was by comparison of its U.V. spectrum with that of similar compounds such as (CCII) that the formula of perhydro-l,3,5-thiadiazine-2-thione (CCIV) was established, which accounts quite well for its properties. It is accepted... 

The rules for quasi-chemical reactions are the same as for the normal chemical reactions, namely mass balance and electroneutrahty conditions one extra requirement appears, however, for crystalline solids where the ratio of sites in the crystal structure should be constant and should satisfy to stoichiometric formula. This means that if, for instance, in the AB2 crystal one site for A atom is formed, then automatically two B-sites appear as well, regardless of their occupancy. It should be noted that the point defects and/or the processes of their formation can also classified into two groups, namely stoichiometric and nonstoichiometric. The first type of process does not disturb the stoichiometric ratio of components constituting the crystal, which is a closed thermodynamic system the second type leads to nonstoichiometric compounds by exchanging components between the... 

In conclusion, the completed X-ray crystallographic studies on the structure of strychnine salts from two laboratories have been published (299, 300) and find themselves in complete agreement with the formula derived by chemical means and now synthesized. The conformational conclusions from these sources are best summarized, and the singular intricacy of the strychnine architecture pictorialized, in the following expression ... 

The same phosphazo-phosphonyl compound MeONP2Cl4 results from the reaction of either phosphorus pentachloride and ethyl P-methyl phosphon-amidate or methyltetrachlorophosphorane and diethyl phosphoramidate (EtO)2P(0)NH2, and although the structure could not be determined by chemical means, formula (80) rather than the isomeric (81) is suggested by C1 n.q.r. measurements. ... 

Condensation polymers, in which the molecular formula of the structural unit (or units) lacks certain atoms present in the monomer from which it is formed, or to which it maybe degraded by chemical means, and addition polymers, in which the molecular formula of the structural unit (or units) is identical with that of the monomer from which the... 

AED provides molecular confirmation by means of its ability to calculate the molecular formula by means of the responses obtained on the simultaneously monitored specific element channels. It is worth noting that sensitivity is tuned according to the chemical element monitored (e.g., acephate is characterized by a 5ng detection limit when monitoring the nitrogen channel, 3ng for phosphorous, 10 ng for oxygen, and 0.3 ng for sulfur). 

Discrete Organic Chemical means any chemical belonging to the class of chemical compounds consisting of all compoimds of carbon except for its oxides, sulfides and metal carbonates, identifiable by chemical name, by stmctural formula, if known, and by Chemical Abstracts Service registry number, if assigned. 

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