CH ENGR 104C Lecture Notes - Lecture 26: Magnetic Anisotropy, Chemical Shift, Atomic Nucleus

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7 Feb 2017

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Nmr or nuclear magnetic resonance spectroscopy is a technique used to determine a compound"s unique structure. It identifies the carbon-hydrogen framework of an organic compound. Using this method and other instrumental methods including infrared and mass spectrometry, scientists are able to determine the entire structure of a molecule. In this discussion, we will focus on h nmr or proton magnetic resonance. Even though there are many other spectrometers including c-nmr and n-nmr, hydrogen (h-nmr) was the first and is the most common atom used in nuclear magnetic resonance spectroscopy. The atomic nucleus is a spinning charged particle, and it generates a magnetic field. Without an external applied magnetic field, the nuclear spins are random and spin in random directions. But, when an external magnetic field is present, the nuclei align themselves either with or against the field of the external magnet. _-spin state: protons that align with the external magnetic field.

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?______________________________________________

CH ENGR 104C Lecture Notes - Lecture 26: Magnetic Anisotropy, Chemical Shift, Atomic Nucleus

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