Question

im not really sure how to predict chemical shift i know the more electronegative the more downfield it will be is there an equation or something? please help me with this problem

1) These molecules have different 'H NMR chemical shifts of the methylene group. Look at the data: 2.6 3.6 1.4 CHE "SH OH Based on this trend, rank order the following molecules in terms of chemical shift (most downfield to most upfield), and estimate the proton chemical shift of the methylene groups (CH) in each. Your answer should reference the locations of the heteroatoms on the Periodic Table NH2

Answer 1

4.601 3.505 3.05 09 NHA most downfield - most upfield & most downfield means it requires higher external magnetic field for the resonance & most upfield means it requires lower external magnetic field for the resonance * Due to this chemical shift values changes. * If more electronegative group is attached to proton attached carbon the it has higher chemical shift Here and si- F IS is most electronegative least electronegative, - As we go left to right in penodic table electronegativity increases - Hence F more electronegative than N. and as we go from top to bottom in goong electronegativity decreases hence F more electronegative than cl

Electronegativity terend F > Cl > N > si is Hence above trend NMR spectrums of each seen in compound