Question

13C NMR Signal and Chemical Shift tural abundance of the ich is 99.985% of hydrogen Sassi The isotope 18C is another NMR active nucleus. The natural abundance isotope is only 1.1% of carbon atoms compared to the 'H isotope which is 99.985% of atoms. Therefore the intensity of WC peaks is lower. It takes a longer time to obtain a spectrum compared to a 'H NMR spectrum. Adjacent WC - WC splitting does occur. chance of two "C atoms being adjacent to each other is so low that splitting is not obse Eoch non-equivalent carbon will give rise to its own signal. Let's look at the C NMR of toluene. There is a plane of symmetry which makes some of the carbons equivalent. Equivalent carbons will produce the same signal. Therefore, toluene will only produce five C NMR signals even though it has seven carbons. Plane of Symmetry toluene The factors that most affect the 13C NMR chemical shifts are: 1. The electronegativity of the groups attached to the carbon signals be 2. The hybridization of the carbon. 150 140 150 120 110 100 90 70 60 50 40 30 20 10 Page 112

Answer 1

june 2Wednesday 3 13 5 C3 NMR Signa 2 2 O-50 PPm 2 50-100 PPm 4 i00-150 Ppm 50-220 PPym 22 Thursday