(BQ) Part 2 book "A Handbook of spectroscopic data chemistry" has contents: 13C NMR spectroscopy, mass spectrometry, structural data obtainable from different spectra. Please refer to the content. | 4 13e NMR Spectroscopy : The 13C chemical shifts of Linear and Branched Alkanes: Alkane groups unsubstituted by heteroatoms absorb downfield from TMS to about 60 ppm. (Methane absorbs at ppm upfield from TMS.) Within this range we can predict the chemical shifts of individual 13C atoms in a straight chain or branched chain hydrocarbon from the data in Table and the formula b = + LnA. Where b = Predicted shift for a carbon atom. A = Additive shift parameter. n = number of carbon atoms for each shift parameter ( is the shift of the i3C of methane). The calculated (and observed) shifts for the carbon atoms of 3-methylpentane are /+ () 6 CH 3 I I CH 3 - I + (+) 2 3 CH 2 - CH- CH 2 - \ + (+) 4 " + (+ ) 5 CH 3 100 Spectroscopic Data Chemistry For carbon atom I, we have la, ° = + ( 1 x I) + ( x I~-, 2y and 1&-carbon atoms. I) + ( x 2) + ( x I) = + Carbon atom 2 has 2 a-, 2 ~-, and 1 y carbon atoms. Carbon atom 2 is a 2° carbon with a 3° carbon attached [2°(3°) = - ] ° 2 = + ( x 2) + ( x 2) + ( x 1) + ( x 1) = Carbon atom 3 has 3 a- and 2 ~- carbon atoms, and it is a 3° atom with two 2° atoms attached [3° (2°) = ]. Thus 03 = + ( + ( x x 3) + ( x 2) 2) = + Carbon atom 6 has, I a-, 2~-, and 2y carbon atoms, and it is a 1° atom with a3° atom attached [10 (3°) =]. Thus, +()+( x °= +( x 1)+( x 2) 6 1)=+ The agreement for such calculations is very good. It is essential that the reference compounds used for such additivity culculations be structurally similar to thecompound of interest. Table : The \3C shift parameters in some linear and branched hydrocarbons 13C Atoms Shift (ppm) (A) a + p + Y b E + + 1° (3? 1° (4°)" 20 (3 o)a 20 (4°) 3° (2°) 3° (3°) 4° (10) 4 ° (2°) 101 I3C NMR .
