IGNOU CHE 10 2016 - Which factors affect the chemical shift? Explain.

Question

Which factors affect the chemical shift? Explain.

26 Oct 2017

Answer :

Word Count : 356

Important factors influencing chemical shift are electron density, electronegativity of neighboring groups and anisotropic induced magnetic field effects.

Electron density shields a nucleus from the external field. For example, in proton NMR the electron-poor tropylium ion has its protons downfield at 9.17 ppm, those of the electron-rich cyclooctatetraenyl anion move upfield to 6.75 ppm and its dianion even more upfield to 5.56 ppm.

A nucleus in the vicinity of an electronegative atom experiences reduced electron density and the nucleus is therefore deshielded. In proton NMR of methyl halides (CH3X) the chemical shift of the methyl protons increase in the order I < Br < Cl < F from 2.16 ppm

______ _________ __________ ____ ___ __________ __________ _________.
_______ __________ ____ _________ _____ ______.
_________ _________ _____ _______ ______ _______ __________ _______.
_____ _____ ____ _________ _________ ___ ___ ________ __________ ____ __________.
_________ _________ _______ _____ ______.
____ _________ ________ _____ ____ ____.
___ ___ _____ _______ __________ _________ ____ _________ ______ ________.
__________ _____ _____ _________ _____ ______ ________ _________ ______ ___.
______ __________ _______ _________ __________.
________ __________ _______ ________ ___ ________ __________ _____ ___ ________ ________.
_______ ______ _______ ____ __________.
__________ ______ _____ __________ ______ __________.
________ _________ ________ _________ ________ ______.
__________ ___ __________ _________ _______ ____ ____.
_________ __________ ___ ________ ________ ________ ____.
___ ______ _____ _____ _________ ________ ___.
_______ ______ ______ ____ _______ _______ _______ _________ ________ ________ ____.
___ ___ ______ __________ ___ ______ _____.
__________ ______ _________ ________ ___ _____ ___ ____ _____.
________ _________ ____ ____ __________ ________.
__________ __________ _______ ____ ______ ______.
________ ______ __________ ________ ________ ___ _____ _________ _____.
____ _____ _______ _____ __________ ___ ___ ________ _________.
_____ __________ ___ _________ _________ _________ _____ ______ ________ ______ ___ ____.
___ __________ ______ __________ _____ __________ ______.
____ __________ _______ _______ _____ ____ ________.
________ ______ ______ _________ _____ _________ ______ ______ _____.
____ _________ _______ _________ _________ ________ _______ ________ __________ __________ ____ ____.
__________ _______ _________ ______ ______ ___ _________ _____ ___ __________ _______.
___ ______ ____ ___ _________ _____ ______ ____ _____ ______ _________ ___.
________.

IGNOU ACADEMY

Your IGNOU journey, made easier.

Solved Assignments
Study Notes
Guess Papers
Question Papers

Call Us WhatsApp

STUDY • PREPARE • SUCCEED

Skip in 10