Alkanes alkynes

Alkane molecules can interact in this way and the strength of the interaction increases with the size of the alkane molecule, van der Waals interactions are also important for alkanes, alkynes and aromatic rings. 

Alkynes are compounds that have a carbon-carbon triple bond. As was discussed in Chapter 3, a triple bond is composed of one sigma bond and two pi bonds. Each triple bond in an alkyne causes it to have four fewer hydrogens than the corresponding alkane. Alkynes are unsaturated compounds. 

T A. Kerr and M. J. Parsonage, Evaluation of Kinetic Data on Gas-phase Addition Reactions Reactions of Atoms and Radicals with Alkanes, Alkynes and Aromatic Compounds, Butterworths, London, 1972. 

Like the alkenes, the alkynes are unsaturated and more reactive than the alkanes. Alkynes can add two molecules of halogen across the triple bond ... 

The resting state (MMOoxd) is reduced back to the diferrous form to close the cycle. In addition to methane, many other substrates react with MMO. These include long-chain alkanes, alkenes, halogenated and other substituted alkanes, alkynes, sulfides, and others. 

Alkynes also undergo a reaction that has no analogy in alkene chemistry. Because a C - H bond of an alkyne is more acidic than a C - H bond in an alkene or an alkane, alkynes are readily deprotonated with strong base. The resulting nucleophiles react with electrophiles to form new carbon-carbon o bonds, so that complex molecules can be prepared from simple starting materials. The study of alkynes thus affords an opportunity to learn more about organic synthesis. 

Finally, it should be pointed out that the oxidation of certain hydrocarbons can produce aerosols even in the absence of S02. Grosjean (1977) has reviewed organic particulate formation. Smog-chamber experiments have shown that straight-chain alkanes, alkynes, and carbonyl compounds... 

TABLE 4. 8. The thermochemistry of the C=C bond 479 Excess heats of mixing -alkane + -alkyne, tetrachloromethane + -alkyne at 298.15 K ... 

ALKENES These contain only carbon and hydrogen. There are four main types Alkenes, Alkanes, Alkynes, and Aromatic hydrocarbons. Contain double bonds between carbon atoms. 

It is very well documented that the carbon-carbon triple bonds (e.g., alkynes) on catalytic hydrogenation gives the completely reduced product, viz. alkanes. Alkynes can also be reduced partially to give z-alkenes by palladium-calcium carbonate catalyst which has been deactivated (partially poisoned) by the addition of lead acetate (Lindlar catalyst) or Pd-BaSO deactivated by quinoline. The lead treatment poisoned the palladium catalyst, rendering it less active and the reaction is more selective. Some examples are given (Scheme 98). 

The occurrence of organic compounds within trench sediments was also assessed as part of the DOE-RL study (1990). The presence of organic compounds in sediments/soils is important because they can form complexes with radionuclides, thus enhancing their mobility. Specific compounds were identified, including alkenes, alkanes, alkynes, elemental sulfur, and three cyclic sulfur species. Organic constituent concentrations are presented in Table 5-17. 

C. Classify alkenes, alkanes, alkynes, and aromatic hydrocarbons as either saturated or unsaturated. 

Compound Wpes Mass values Alkanes Alkenes, Mono- cyclo- alkanes Alkynes, Dienes, Cyclo- alkenes Poly- cyclic alicycles Alkanones, Alkanals Alcohols, Alkyl ethers Cyclic alcohols Cyclo- alkanones Aliphat.. acids. Esters, Lactones Alkyl- amines... 

Table 7.1 Rate constants of reactions of alkanes, alkynes and aromatic hydrocarbons with OH at 298 K...

Alkenyl hydrogens (and carbons) are deshielded and give rise to relatively low-field NMR signals compared with those in saturated alkanes (Section 11-4). In contrast, alkynyl hydrogens have chemical shifts at relatively high field, mnch closer to those in alkanes. Similarly, the sp-hybridized carbons absorb in a range between that recorded for alkenes and alkanes. Alkynes, especially terminal ones, are also readily identified by IR spectroscopy. Finally, mass spectrometry can be a useful tool for identification and structure elucidation of alkynes. 

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