nmr and chromatagrophu

Question 1

What is NMR spectroscopy ?

Answer 1

-nmr is a technique used to find the structure of organic compounds. it depends on the ability of nuclei to resonate in a magnetic field due to an odd number of nucleons creating a residual spin

Question 2

explain the whole process of nmr? (not in spec but for info)

Answer 2

• if nuclei that have magnetic properties are subjected to a strong magnetic field , they can either align themselves in the same direction as the magnetic field (a low energy state) or in the opp direction (high energy state)
• when these nuclei are then subjected to radio-waves with a range of frequencies, each nucleus can absorb the frequency which corresponds to the difference in energy between its low-energy state and it’s high energy state.
• the frequency of the radiation absorbed by the nuclei varies depending on the type of nucleus and thus can be used to provide important structural information about the molecule.

Question 3

What is C-13 nmr spectroscopy?

Answer 3

-investigates the absorption of radiation by nuclei of Carbon-13 atoms and is thus a technique for obtaining information about the number and arrangements of carbon atoms in a molecule.

Question 4

what is chemical shift?

Answer 4

Is a number that indicates it’s behaviour in a magnetic field relative to TMS. It can be used to identify the chemical environments of the carbon or hydrogen atoms attached to it.

Question 5

What solvents are used for NMR

Answer 5

CCl4 or CDCl3. (D stands for deuterium 2H - 1 protons and 1 neutron)

Question 6

Why is it necessary to use solvents that don’t contain hydrogen?

Answer 6

Hydrogen atoms absorb radiation and therefore interfere with the spectrum