Density of organic compounds

Critically evaluated experimental data covering the densities of organic compounds is essential for both scientific and industrial applications. Knowledge of densities is important in many areas, including custody transfer of materials, product specification, development of various predictive methods, and for characterizing compounds and estimating their purity. 

Applicability Saturated liquid densities of organic compounds. 

The density of organic compounds RX increases in the order X = Hcarbon atom decreases in the order of first > second > third > fourth [19]. 

Location of the compound within a class (or homologous series) of compounds. Reference to the literature or to tables of the physical properties of the class (or classes) of organic compounds to which the substance has been assigned, will generally locate a number of compounds which boil or melt within 6° of the value observed for the unknown. If other physical properties e.g., refractive index and density for a hquid) are available, these will assist in deciding whether the unknown is identical with one of the known compounds. In general, however, it is more convenient in practice to prepare one, but preferably two, crystalhne derivatives of the substance. 

Separations based upon differences in the physical properties of the components. When procedures (1) or (2) are unsatisfactory for the separation of a mixture of organic compounds, purely physical methods may be employed. Thus a mixture of volatile liquids may be fractionally distilled (compare Sections 11,15 and 11,17) the degree of separation may be determined by the range of boiling points and/or the refractive indices and densities of the different fractions that are collected. A mixture of non-volatile sohds may frequently be separated by making use of the differences in solubilities in inert solvents the separation is usually controlled by m.p. determinations. Sometimes one of the components of the mixture is volatile and can be separated by sublimation (see Section 11,45). 

Di is equal to read from Fig. 2-38 if Z > 0.27 and Di is eqiial to Di, read from Fig. 2-39 if Z < 0.27. At reduced temperatures less than 0.9, Dj can be taken as 0. The density is then c culated from Eq. (2-76). All families of organic compounds except mercaptans and carboxylic acids are predicted within an average deviation of 5 percent. 

Various compilations of densities for organic compounds have been published. The early Landolt-Bomstein compilation [23-ano] contained recommended values at specific temperatures. International Critical Tables [28-ano-l] provided recommended densities at 0 °C and values of constants for either a second or third order polynomial equation to represent densities as a function of temperature. This compilation also gave the range of validity of the equation and the limits of uncertainty, references used in the evaluation and those not considered. This compilation is one of the most comprehensive ever published. Timmermans [50-tim, 65-tim], Dreisbach [55-die, 59-die, 61-dre] and Landolt-Bomstein [71-ano] published additional compilations, primarily of experimental data. These compilations contained experimental data along with reference sources but no estimates of uncertainty for the data nor recommended values. 

The reactivity of organic compounds toward eh varies systematically (Hart and Anbar, 1970), the variation often attributable to electron density of a specific functional group. Other generalizations are the following ... 

Chain processes, free radical, in aliphatic systems involving an electron transfer reaction, 23,271 Charge density-NMR chemical shift correlation in organic ions, 11,125 Chemically induced dynamic nuclear spin polarization and its applications, 10, 53 Chemiluminescence of organic compounds, 18,187... 

The important physical properties of organic compounds include melting and boiling points and solubility and density. Whenever you compare physical properties of different compounds, stick to compounds with similar molecular weights. 

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