Formulas of organic compounds

Molecular formulas of organic compounds are customarily presented in the fashion C2H5Br02 The number of carbon and hydrogen atoms are presented first followed by the other atoms in alphabetical order Give the molecular formulas corresponding to each of the compounds in the preceding problem Are any of them isomers ... 

In Section F, we saw that one technique used in modern chemical laboratories to determine the empirical formulas of organic compounds is combustion analysis. We are now in a position to understand the basis of the technique, because it makes use of the concept of limiting reactant. 

In Section F, we remarked that one technique used in modern chemical laboratories or the agencies that carry out contract work on behalf of other chemists is combustion analysis. This technique—which has been used since the earliest days of chemistry—is used to establish the empirical formulas of organic compounds and, in combination with mass spectrometry, their molecular formulas. It is used both for newly synthesized compounds and to identify active compounds in natural products. We are now in a position to understand the basis of the technique, for it makes use of the concept of limiting reactant. 

Le Bel, On the Relations which Exist between the Atomic Formulas of Organic Compounds and the Rotatory Powers of their Solutions (1874), reprinted in O. T. Benfey, Classics in the Theory of Chemical Combination (New York Dover, 1963), 161. 

An older nomenclature system used the name of the radical (the name of the parent hydrocarbon with the -yl ending) plus the word alcohol. Thus, ethanol is also known as ethyl alcohol and, because it is the most familiar alcohol, even simply as alcohol. The formulas of organic compounds can be written in the reverse direction, so ethanol can be represented by HOCH2CH3, as well as by CH3CH2OH. 

Carbon content is obtained from CHN analysis of modified adsorbent sample. This analysis is usually based on the determination of the amount of CO2 gas produced after combustion of the sample of known weight in the oxygen atmosphere— the standard procedure for the determination of the bulk formula of organic compounds. In contrast to the organic compounds. 

Le Bel published his stereochemical ideas two months later, in November 1874, under the title, The relations that exist between the atomic formulas of organic compounds and the rotatory power of their solutions" (14). An English translation is presented in Le Bel (15). Le Bel approached the problem from a different direction from van t Hoff. His hypothesis was based on neither the tetrahedral model of the carbon atom nor the concept of fixed valences between the atoms. He proceeded purely from symmetry arguments he spoke of the asymmetry, not of individual atoms, but of the entire molecule, so that his views would nowadays be classed under the heading of molecular asymmetry. Only once does he mention the tetrahedral carbon atom, which he regarded as not a general principle but a special case. Today, substituted allenes, spiranes, and biphenyls are but a few examples of asymmetric molecules that do not contain any asymmetric carbons, thus confirming Le Bel s views on molecular asymmetry. The reason for the different approaches by van t Hoff and le Bel is easy to understand, van t Hoff came from the camp of structural chemists, and he... 

J. A. Le Bel, On the relations which exist between the atomic formulas of organic compounds and the rotatory power of their solutions, Tlic Foundations o/ Stereo Chemistry Memoirs by Pasteur, Van t Hoff, Le Bel, and Wislicenus (G. M. Richardson, ed.), American Book Co., New Ybrk, 1901, pp. 49-59,... 

Volumes 28 and 29 of the Second Supplement are, respectively, the subject and formula indexes to the entire "Beilsteins Handbuch the three-part cumulative formula index, arranged by the Hill system, is the only index recording the known formulas of organic compounds from the beginnings of organic chemistry through 1929. (The Chemical Abstracts cumulative formula index extends this period to 1946.)... 

On the Relations Which Exist between the Atomic Formulas of Organic Compounds and the Rotatory Power of Their Solutions... 

PeDegrin, V. (1983) Molecular formulas of organic compounds. The nitrogen rule and degree of unsaturation. J. Chem. Educ., 60, 626-633. 

Figure 3.5 Combustion apparatus for determining formulas of organic compounds. A sample of compound that contains C and H (and perhaps other elements) is burned in a stream of O2 gas. The CO2 and H2O formed are absorbed separately, while any other element...

In a similar fashion, quantitative elemental analysis for carbon, hydrogen, nitrogen, and oxygen enabled the chemist to determine the empirical formulas of organic compounds. An empirical formula is the simplest whole number ratio of the atoms of each element present in a molecule. For any given compound, the empirical formula may or... 

Therefore in order to calculate the molecular formula of a compound it is necessary to know its molar mass. Molar masses can be determined by a variety of physical measurements, including back titrations (for weak acids and bases) and weighing gases. Mass spectrometry is frequently used to determine the molar masses of molecular substances (Chapter 2). Automated instruments for determining the empirical and molecular formulas of organic compounds are available. 

The structural formulas of organic compounds can be determined by nuclear magnetic resonance (NMR) and mass spectrometry (Chapter 21). 

What is the difference between molecular formulas and structural formulas of organic compounds ... 

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