Homologous series alkanes

Problem 1.13 Methane, CH ethane. C,H and propane. C,are the first three members of the alkane homologous series. By what structural unit does each member differ from its predecessor -4... 

This series of daughter ions differing in their mass by 14 is characteristic of the straight-chain alkanes (homologous series differing by a CH2 group). 

At this point it should be remarked that multivariate regression with latent variables is a useful tool for describing the relationship between complex processes and/or features in the environment. A specific example is the prediction of the relationship between the hydrocarbon profile in samples of airborne particulate matter and other variables, e.g. extractable organic material, carbon preference index of the n-alkane homologous series, and particularly mutagenicity. The predictive power was between 68% and 81% [ARMANINO et al., 1993]. VONG [1993] describes a similar example in which the method of PLS regression was used to compare rainwater data with different emission source profiles. 

Q 029 List the roots used to name the first ten members of the alkane homologous series. Indicate the number of carbon atoms that each represents. 

Figure 2 shows values of the critical temperature and critical concentration in nitrobenzene - -alkanes homologous series. Noteworthy is the power-type evolution of the critical concentration, described by the power exponent 1/2. The pressure dependence of the critical consolute temperature for these critical mixtures are shown in Fig. 3. Noteworthy is the change of the sign from dT(2 jdP < 0 to dT jdP > 0 when increasing the length of -alkane.

Errington JR, Panagiotopoulos AZ (1999) A new intermolecular potential model for the n-alkane homologous series. J Phys Chem B 103 6314-6322... 

Fig. X-9. Zisman plots of the contact angles of various homologous series on Teflon O, RX , alkylbenzenes (f), n-alkanes , dialkyl ethers , siloxanes A, miscellaneous polar liquids. (Data from Ref. 78.)...

Unbranched alkanes of the type CH3(CH2) cCH3 are often referred to as n alkanes and are said to belong to a homologous series... 

In fact, this procedure can be used for any aliphatic series such as alcohols, amines, etc. Consequently, before dealing with a specific homologous series, the validity of using the methylene group as the reference group needs to be established. The source of retention data that will be used to demonstrate this procedure is that published by Martire and his group [5-10] at Georgetown University and are included in the thesis of many of his students. The stationary phases used were all n-alkanes and there was extensive data available from the stationary phase n-octadecane. The specific data included the specific retention volumes of the different solutes at 0°C (V r(To)) thus, (V r(T)) was calculated for any temperature (Ti) as follows. 

Fig. 17. An homologous series of alkane probes is generally used because good values for their adsorbed molar areas are available [87]. The linearity of the plot (the alkane line ) lends credence to the procedure.

Table 2.3 lists the heats of combustion of several alkanes. Unbranched alkanes have slightly higher heats of combustion than their 2-methyl-branched isomers, but the most important factor is the number of carbons. The unbranched alkanes and the 2-methyl-branched alkanes constitute two separate homologous series (see Section 2.9) in which there is a regular- increase of about 653 kJ/mol (156 kcal/mol) in the heat of combustion for each additional CH2 group. 

Alkenes also form a homologous series as the carbon number increases, the number of possible isomeric structures for each member increases more rapidly than in the case of the alkane series. 

In the homologous series of alkane 1-sulfonates, micellization in aqueous solutions begins with the pentanesulfonate at cM = 1 mol/L. The critical micelle concentrations of the technical alkanesulfonates are cM = 0.002 mol/L (sulfo-chlorination route) and cM = 0.44 g/L (sulfoxidation route). 

Detectability may be a significant problem with homologous series of unsaturated compounds, particularly //-alkanes. For these compounds, refractive index detection or evaporative light-scattering, both of which are described elsewhere in the book, may be of use. Indirect photometry is a useful detection scheme for compounds that do not absorb in the UV. Acetone, methylethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, and acetophenone are added to an acetonitrile/water mobile phase, generating a negative vacancy peak when the nonchro-mophoric analyte emerges and a positive peak if the ketone is adsorbed and displaced.70 Dodecyl, tetradecyl, cetyl, and stearyl alcohols also have been derivatized with 2-(4-carboxyphenyl)-5,6-dimethylbenzimidazole and the derivatives separated on Zorbax ODS in a mobile phase of methanol and 2-propanol.71... 

Their hydrophobicity and their plasticity were appreciated and used for a long time in a wide range of activities. To our knowledge, the first wax to have been exploited is beeswax. Beeswax is produced by various species of bees in the world, and it has a melting point between 62°C and 64°C. It mainly contains homologous series of even-numbered fatty acids (C22 C34, C2 being the predominat compound), odd-numbered ra-alkanes (C2i C33, C27 being the major compound) and even-numbered palmitic esters from C40 to C52 (Tulloch and Hoffman, 1972 Kolattukudy, 1976). Hydroxy esters, diesters and hydroxy diesters also form part of beeswax to a lesser extent. 

Waggott [57] reported that a factor of major concern in adapting the technique to more polluted samples is the capacity of the carbon filter, which usually contains only 1.5-2 mg carbon. He showed that the absolute capacity of such a filter for a homologous series of 1-chloro-n-alkanes was 6 xg for complete recovery. Maximum recovery was dependent on carbon number, being at a maximum between Cs and C12 for the 1-chloro-n-alkane series. It is important, therefore, to balance the amount of sample stripped with the capacity of the carbon filter to obtain better than 90% recoveries. 

These four molecules are the first four members of the alkanes, a homologous series of saturated hydrocarbons with the general formula, C H2 +2. The difference between them is in the number of C atoms in the compound the formula of each alkane differs from the next by one CH2 group. 

There are many bicyclic dienes and polyenes. If for no other reason than to show that seemingly homologous series often show profound complications, in Table 3 we present the enthalpies of formation of the bicyclo[2.2.n]alka-2,5-dienes, bicyclo[2.2.n]alk-2-enes and bicyclo[2.2.n]alkanes, species 68, 69 and 70, respectively, wherein we limit our attention to the cases of n = 0, 1 and 2. It is seen that the enthalpies of formation of the bicycloalkadiene, bicycloalkene and bicycloalkane always become more negative in that... 

The alkanes make up a homologous series of hydrocarbons with the general formula C H2 +2 in is the number of carbon atoms). Alkanes exhibit a type of structural isomerism called chain isomerism, where the arrangement of the carbon atoms in the molecules is different. 

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