If you were to hydrogenate a -CH=CH- bond (making it a -CH_2-CH_2- bond), what should happen to...

Question:

If you were to hydrogenate a -CH=CH- bond (making it a -CH_2-CH_2- bond), what should happen to the 13C-NMR signal for these carbons

13-C NMR:


13-C NMR is the application of nuclear magnetic resonance spectroscopy to study the carbon nucleus. This form of NMR targets the 13-C isotope because the 12-C isotope is not detectable (no spin). In combination with other tools like 1-H NMR and Infrared (IR) Spectroscopy, it is used to determine the structure of organic compounds, based on peaks (signals) corresponding to atoms with a unique chemical environment.

Answer and Explanation:


This hydrogenation reaction represents a reduction of sp2 carbons to sp3 carbons. The chemical shift range for alkene (sp2) carbons with hydrogens attached is approximately 120-160 ppm (relative to TMS = tetramethylsilane standard). After hydrogenation to an alkane (sp3) carbon with hydrogens attached, these carbons will drop to a chemical shift range of 10-50 ppm in their NMR spectrum. If both of these carbons are chemically unique then you will see 2 peaks performing this transition.


Learn more about this topic:

Nuclear Magnetic Resonance Spectroscopy: C-13 vs 1H
Nuclear Magnetic Resonance Spectroscopy: C-13 vs 1H

from AQA A-Level Chemistry: Practice and Study Guide

Chapter 17 / Lesson 2
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