Hydrocarbon compounds melting points

As noted above, Carlson et al. (1993) initially identified the presence of monocyclic/acyclic branched alkanes in the high molecular weight fractions. More recently Hsieh et al. (2000) noted the presence of alkylaromatic compounds in this fraction along with a wide variety of branched hydrocarbons, alkylcyclohexanes and alkylcyclopentanes. However, the need to document the identities of all the compounds completely cannot be over-emphasized. Physical properties of the branched hydrocarbons, particularly melting points, vary significantly with... 

Picrates, Picric acid combines with amines to yield molecular compounds (picrates), which usually possess characteristic melting points. Most picrates have the composition 1 mol amine 1 mol picric acid. The picrates of the amines, particularly of the more basic ones, are generally more stable than the molecular complexes formed between picric acid and the hydrocarbons (compare Section IV,9,1). 

An operator had to drain water from a 1,200-m spherical storage vessel nearly full of propane (Figure 8-1). He opened valves A and B. When traces of oil showed that the draining was nearly complete, he shut A and then cracked it to complete the draining. No flow came. He opened A fully. The choke—presumably hydrate, a compound of water and a light hydrocarbon with a melting point above 0°C—cleared suddenly, and the operator and two other men were splashed with liquid. The handle came off valve A, and they could not get it back on. Valve B was frozen and could not be moved. Access was poor because the drain valves were immediately below the tank, which was only 1.4 m above the ground. 

The above considerations indicate the complex nature of the hydrocarbons known as caryophyllene. For practical purposes, however, the compounds indicated are obtained of practically definite melting-points, and, in spite of the complicated isomerism existing amongst most of them, are useful for identification of the sesquiterpene or mixture of sesquiterpenes, occurring naturally and known as caryophyllene . 

These compounds are chemically and thermally stable and strain-free. These characteristics cause high melting points (m.p.) in comparison to other hydrocarbons. For instance, the m.p. of adamantane is estimated to be 269 °C, yet it sublimes easily, even at atmospheric pressure and room temperature. The melting point of diamantane is about 236.5 °C and the melting point of triamantane is estimated to be 221.5 °C. The available melting point data for diamondoids are reported in Table I. 

Separation can also be accomplished by solvent extraction, adsorption, and crystallization. Solvent extraction is accomplished by selectively dissolving certain hydrocarbon components. Adsorption is similar to solvent extraction but uses a solid to separate out various components selectively based on their tendency to adhere to the surface of the solid adsorbent. Crystallization uses the differing melting points of the components during cooling, which causes some of its compounds to solidify or crystallize, and separate out of the liquid. 

Compound 19 (R = Me, R = H) produced in the above reaction differs slightly in melting point (122° and 116°-117°, respectively) from the dimethylthienothiophene (17) obtained by Friedmann. This supports Horton s assumption that the action of sulfur on the linear Cg hydrocarbons is more likely to lead to thienothiophene 19 (R = Me, R = H) than to its isomer (17), the formation of the latter requiring a deep-seated rearrangement of the skeleton. 

Nitro compounds. Aliphatic nitro compounds are acidic. They are freed from alcohols or alkyl halides by standing for a day with concentrated sulphuric acid, then washed with water, dried with magnesium sulphate followed by calcium sulphate and distilled. The principal impurities are isomeric or homologous nitro compounds. In cases where the nitro compound was originally prepared by vapour phase nitration of the aliphatic hydrocarbon, fractional distillation should separate the nitro compound from the corresponding hydrocarbon. Fractional crystallisation is more effective than fractional distillation if the melting point of the compound is not too low. 

Many textbooks still state that organic lithium compounds have appreciable covalent character. This misconception arises from physical properties such as relatively low melting points and solubility in hydrocarbons or other nonpolar solvents. It is true that these properties... 

The classes listed in Table 1-12 are families which exhibit the same regularity of boiling points, melting points, densities, and other properties seen in the hydrocarbon families we have already studied. Some of the families are named with characteristic suffixes while others have prefixes, or even separate words-in the names. For instance, alcohols are named with the suffix -ol. Ketones are named with the suffix -one. Amine and nitriles are named with the full suffix according to the family name. Ethers and halides usually have the full family name as a separate word, and nitro- and organometallic compounds have the prefix nitro- or the prefix corresponding to the hydrocarbon part of the organometallic molecule. 

The melting points and boiling points of carboxylic acids are higher than those of hydrocarbons and oxygen-containing organic compounds of comparable size and shape and indicate strong intermolecular attractive forces. 

Tris[bis(trimethylsilyl)amido]uranium is an extremely air- and moisture-sensitive, red-purple solid, which can be stored for months in the absence of air and moisture without noticeable signs of decomposition. It is soluble in both aliphatic and aromatic hydrocarbons. The NMR spectrum in benzene- (250 MHz, 20°C) shows a single broad resonance at d — 11.5.11 The compound sublimes readily at 80°C under good vacuum (10 6 torr). The checkers report a melting point of 137-140°C. The IR spectrum, recorded as a Nujol mull between KBr plates, has absorptions at 1248(s), 1170(w), 990(s), 860(s), 828(s), 764(m), 676(m), 654(m), and 598(m) cm1. Other physicochemical properties are described in the literature.4... 

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