Unsaturated hydrocarbon physical properties

Chakactkrisation of Unsaturatkd Aliphatic Hydrocarbons Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are soluble in concentrated sulphuric acid and exhibit characteristic reactions with dUute potassium permanganate solution and with bromine. Nevertheless, no satisfactory derivatives have yet been developed for these hydrocarbons, and their characterisation must therefore be based upon a determination of their physical properties (boiling point, density and refractive index). The physical properties of a number of selected unsaturated hydrocarbons are collected in Table 111,11. 

The physical properties of the fatty acids, and of compounds that contain them, are largely determined by the length and degree of unsaturation of the hydrocarbon chain. The nonpolar hydrocarbon chain accounts for the poor solubility of fatty acids in water. Laurie acid (12 0, Mx 200), for example, has a solubility in water of 0.063 mg/g—much less than that of glucose (Mt 180), which is 1,100 mg/g. The longer the fatty acyl chain and the fewer the double bonds, the lower is the solubility... 

Terpenes are a class of unsaturated hydrocarbons made up of isoprene C5 units and found in essential oils and oleoresins of plants such as conifers. The two most commonly used as solvents are turpentine and o-limonene. Their physical properties are compared with those of toluene and methylene chloride in Table 5.7. They are both immiscible with water. As can be seen in Figure 5.3, D-limonene and other small terpenes have similar molecular weights and structures to substituted cyclohexanes and toluene and are therefore to likely have solvent properties intermediate between these two VOCs. 

If one considers only hydrocarbons, and more especially the so-called alternant hydrocarbons, i.e. first of all the conjugated polyenes and the aromatic hydrocarbons of the benzene series, the greater part of their physical properties, ionization potentials, lower electronic transitions etc., can be interpreted qualitatively and often quantitatively in terms of the electronic structure of the n system alone. As the number of n electrons is small with respect to the total number of electrons of the molecule, a considerable simplification of the quantum-mechanical problem is obtained. However, it must be noted immediately that the assumptions of a complete a—n separation and of a rigid a frame are not sufficient to eliminate the a electrons completely from the theory because the n electrons of an unsaturated molecule are not attracted by bare nuclei, but are subject to an effective potential containing Coulomb and exchange contributions from the a electrons. 

Diastereomers are also encountered in unsaturated acyclic compounds. When two C atoms are joined together by a double bond, all the remaining four single bonds to the two C atoms lie in the same plane as the C=C bond. If each of these two carbon atoms is bonded to a H atom and a hydrocarbon (alkyl) chain, the alkyl chains can be either on the same side of the C=C bond as each other or on opposite sides, and the resulting diastereomers (which used to be known as geometric isomers), shown in Fig. 2.2b, are termed cis and tram, respectively. Again, these diastereomers have different physical properties (see also Box 2.3). Optical isomerism is not possible about a C=C bond (the mirror images are superimposable). 

Alkenes and alkynes are unsaturated hydrocarbons. Alkenes are characterized by the presence of at least one carbon-carbon double bond and have the general molecular formula C H2 . Alkynes are characterized by the presence of at least one carbon-carbon triple bond and have the general molecular formula C H2 2- The physical properties of the alkenes and alkynes are similar to those of alkanes, but their chemical properties are quite different. 

The chemical modification of sulfur to alter its physical properties for use in land stabilization was investigated. Commercially available, low-cost unsaturated hydrocarbons were used as chemical modifiers. By using modifiers alone or in combination, the properties of sulfur in both the molten and solid state were controlled, permitting its use by either direct penetration or thin crust formation to stabilize tailings. The most suitable formulation was sulfur modified with 6-7% dicyclopentadiene and 1% dipentene. 

Several attempts have been made to replace silver ion with ions of other elements [74, 75]. Of particular practical and theoretical interest is the possibility of using thallium salts [74]. The physical and chemical properties of silver(I) and thallium(I) compounds are similar. Thallium(I) salts are stable up to 150°C in the absence of oxygen, but thallium(I) complexes with unsaturated hydrocarbons have not been studied before. The results of the separation are given in Table 6.1 [74]. 

The physical properties of a fatty acid depend on the length of the hydrocarbon chain and the degree of unsaturation. As expected, the melting points of saturated fatty acids increase with increasing molecular weight because of increased van der Waals interactions between the molecules (Section 2.9). 

PHYSICAL PROPERTIES colorless, limpid liquid aromatic, ether-like odor burning, sweetish taste very soluble in ethyl alcohol freely soluble in water miscible with water, methanol, benzene, acetone, ether, chloroform, carbon tetrachloride, and many unsaturated hydrocarbons immiscible with many saturated hydrocarbons MP (-46°C, -50°F) BP (82°C, 179°F) SG (0.79) DN (0.78745g/mL at 15°C) ST (29.04 dynes/cm at 20°C) VS (0.43cP at 0°C, 0.25cP at 20°C, 0.30cPat 40°C) CP (91.4 J/K mol liquid at 298.15K) HV (313 Btu/lb, 174 cal/g, 7.29 x... 

The physical properties of the alkenes are very similar to those of the alkanes. Chemically, however, they are much more reactive than the alkanes because they contain double bonds. Alkenes are said to be unsaturated hydrocarbons, because of the double bond, their molecules can add on more atoms of hydrogen. The unsaturation of alkenes gives rise to reactions with substances other than hydrogen. The chemical properties of alkenes are as follows ... 

Due to their extensive use in the polymer industry and as solvents, there is a continuing need for better separation processes for alkenes and other unsaturated organic compoimds from alkanes. Perfluorosulfonic acid (PFSA) membranes, such as Nafion (1), that have been ion-exchanged with silver(I) ion exhibit large transport selectivities for many unsaturated hydrocarbons with respect to saturates with similar physical properties. These selectivities are the result of reversible complexation reactions between the unsaturated molecules and Ag+ (2-4), which results in facilitated transport through the membranes (5). 

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