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Isomerism is the phenomenon of the existence of substances with
the same gross formula, but with different physical and chemical
properties. Isomers are compounds having the same qualitative
and quantitative composition but different chemical structures.
For example, the gross formula C 2H 6O is typical for both C 2H 5OH
ethanol and for the dimethyl ester CH 3-O-CH 3, i.e. for two
different compounds with different properties. So, ethanol has a
boiling point of + 78.3 ºС, and a dimethyl ether -24 ºС.
From the structural formulas of these substances it is clear
that this is due to the uneven arrangement (sequence) of atoms in
the molecule relative to one another. Isomers may differ in
structure of the carbon chain, the sequence of bonds between
atoms, the position of functional groups (structural isomerism), or
the placement of atoms (separate groups of atoms) in space
(stereoisomerism). There are also other isomerisms - dynamic
isomerism (tautomerism), optical isomerism. The qualitative
analysis of organic compounds makes it possible to establish their
elemental composition.

Detection of Carbon and Hydrogen

The most common, universal method for detecting the
organic matter of Carbon and, at the same time, it is the
Hydrogen, is the oxidation of the organic matter with the copper
(II) oxide. In this case, Carbon is oxidized to Carbon (IV) oxide,
Hydrogen - to water, and copper (II) black oxide is restored to
cuprum (I) of brown-red or metallic copper oxide. About 0.2-0.3
g of the test substance (sugar, starch, benzoic acid, naphthalene,
etc.) are mixed with 1-2 g of powder of cuprom (II) oxide on a
slide or paper. The mixture is transferred to a dry test tube (1)
(Fig. 1.1).