Preference curve alkane

If homologous oil series other than n-alkanes are employed, a similar shape of preference curve for a given... 

Spectra of branched saturated hydrocarbons are grossly similar to those of straight-chain compounds, but the smooth curve of decreasing intensities is broken by preferred fragmentation at each branch. The smooth curve for the -alkane in Figure 1.14 (top) is in contrast to the discontinuity at C)2 for the branched alkane (Figure 1.14, bottom). This discontinuity indicates that the longest branch of 5-methylpentadecane has 10 carbon atoms. 

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