3.4 - Experimental determination of structure

Question 1

elemental microanalysis is used to determine the masses of what elements

Answer 1

C,H,O,S and N

Question 2

what type of formula does elemental microanalysis determine

Answer 2

empirical

Question 3

what does an empirical formula show

Answer 3

the simplest ratio of the elements in a molecule

Question 4

how can elemental microanalysis be determined

Answer 4

combustion product masses

percentage product by mass

Question 5

mass spectrometry can be used to determine what

Answer 5

the accurate gfm and structural features of an organic compound

Question 6

describe the process of mass spectrometry

Answer 6

a small sample of an organic compound is bombarded by high-energy electrons. This removes electrons from the organic molecule generating positively charged molecular ions known as parent ions. These molecular ions then break into smaller positively charged ion fragments.

Question 7

what is produced by mass spectrometry

Answer 7

a mass spectrum showing a plot of the relative abundance of the ions detected against the mass-to-charge (m/z) ratio

Question 8

infrared spectroscopy is used to identify what in an organic compound

Answer 8

certain functional groups

Question 9

what does infrared radiation do to bonds in an organic molecule when absorbed

Answer 9

causes them to vibrate (stretch and bend)

Question 10

describe the experimental process of infrared spectroscopy

Answer 10

infrared radiation is passed through a sample of the organic compound and then into a detector that measures the intensity of the transmitted radiation at different wavelengths.

Question 11

what is the absorbance of infrared radiation measures in

Answer 11

wavenumbers (cm^-1)

Question 12

what can proton nuclear magnetic resonance spectroscopy give information about

Answer 12

the different chemical environments of hydrogen atoms and how many there are in each of these environments

Question 13

which has higher energy, aligning with a magnetic field or aligning against a field

Answer 13

aligning against it

Question 14

Describe the process of proton NMR spectroscopy

Answer 14

radio wave radiation causes protons to flip from the lower to the higher energy alignment. As they fall back down to the lower energy alignment the emitted radiation is detected and plotted on a spectrum

Question 15

what is the standard reference substance used in proton NMR spectroscopy

Answer 15

tetramethylsilane

Question 16

what is the chemical shift value of tetramethylsilane

Answer 16

0

Question 17

which provides more detailed spectra, high radio frequencies or low radio frequencies