CHEM 228 Chapter Notes - Chapter 13: Chemical Shift, Pi Bond, Propyl Group

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3 Sep 2016

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Nuclear magnetic resonance- the magnetic nuclei are said to be in resonance with the applied radiation. The exact frequency necessary for resonance depends on both the strength of the external magnetic eld, the identity of the nucleus, and the electronic environment of the nucleus. Absorption is not the same for all 1h or all 13c nuclei. Nuclei experience shielding- an effect observed in nmr that causes a nucleus to absorb toward the right side of the chart. Shielding is caused by donation of electron density to the nucleus. The chemical shift: the position on the nmr chart where a nucleus absorbs. Nuclei that absorb on the down eld side of the chart require a lower eld strength for resonance. Nuclei that absorb on the up eld side require a higher eld strength for resonance. *chemical shifts re caused by the small local magnetic elds of electrons surrounding different nuclei.

Related Questions

NMR (nuclear magnetic resonance) Uses the same theory and technology as an MRI!

1-What is the source of energy in NMR?____________________________________ What happens to atoms in a molecule exposed to this energy?_______________________________

2-What are two atom types that can be observed by NMR?________________________

3-What units are used to measure the strength of the magnetic field used?____________________ More significantly for us, what units are used to indicate the frequency of radiation used for resonance?________________

(Our instrument downstairs (a picoSpin) is 45 MHz. At the MN NMR Center at the U, they have instruments ranging 500 â 900 MHz.)

4-What can be distinguished with NMR?______________________________________________________

5-What are the axes of an NMR spectrum?____________________________________________________

6-What are the four different features of a spectrum that can provide information?

7-The number of NMR signals in a spectrum is equal to what?___________________________________

8-The position of an NMR signal in a spectrum depends on the electronic environment surrounding a particular __________________________.

9-If a proton is attached to an electronegative atom, it absorbs (downfield or upfield).

10-Where in an NMR spectrum would we expect to see an aldehyde H? See Table 14.1 ________________

11-What information is given by the area under an NMR signal?____________________________________

12-What information about is given by spin-spin splitting?________________________________________

13-How many peaks are contained in an NMR signal that has been described as a triplet?_________________________ How many adjacent protons are splitting this signal?________________

Skipping to section 14.11â¦

14-What do the number of different signals in a ¹³C spectrum indicate? __________________________________

15-What is the range of chemical shifts in a ¹³C spectrum?______________________________________________

CHEM 228 Chapter Notes - Chapter 13: Chemical Shift, Pi Bond, Propyl Group

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