Structural Analysis 2 Flashcards Preview

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Flashcards in Structural Analysis 2 Deck (18):
1

What is the effect IR radiation on organic compounds

The energy is sufficient to cause bond within the molecule to vibrate.

2

What two factors determine the wavelength of radiation absorbed by the compound?

The type of atom which makes up the bond and the stiffness of the bond

3

What type of energy do:
-Light atoms with stiff bonds absorb
-Heavy atoms with looser bonds?

-Shorter wavelengths
-Longer wavelengths

4

What can IR spectroscopy be used to find?

Certain bonds and functional groups in molecules

5

What state must the material in question be?

Any state

6

How is an infra-red spectrum formed?

The transmitted radiation is passed to a detector which measures the absorbance of IR at different wavelengths of radiation.

7

What is the units at the bottom of the graph?

Wavenumber, units are often cm-1

8

How many directions can a hydrogen proton spin around its own axis?

2

9

What happens when these hydrogen protons are placed between the poles of a powerful magnet?

They act like small magnets. Some align themselves with the field of the magnet, while others align against it.

10

What is the energy difference between protons caused by?

Protons signing with the magnetic field have a slightly lower energy than those aligned against it.

11

What is the difference in energy between the states equal to?

The energy of the radio-frequency part of the electromagnetic spectrum.

12

What happens when the protons which absorb the radio wave radiation?

They are flip from being aligned with the field to being aligned against it

13

What happens as the protons fall back to their lower energy state?

The same radio frequency that was absorbed is emitted. Which can be measured with a radio receiver.

14

What does proton NMR spec give information about?

-The different chemical environments of the protons in an organic molecule.
-How many protons are in each of these environments

15

What is the area under each peak proportional to?

The number of protons in that environment.

16

What does TMS stand for?

Tetramethylsilane

17

What is TMS used for?

It is used as a standard for which all absorptions (due to other proton environments) are measured.

18

What is the chemical shift?

The difference between the protons in TMS and other chemical environments