Experimental Determination of Structure Flashcards Preview

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Flashcards in Experimental Determination of Structure Deck (28)
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1
Q

What is elemental analysis also known as?

A

combustion analysis

2
Q

What is the empirical formula?

A

the simplest ratio

3
Q

What can combustion analysis not give?

A

the percentage of oxygen

4
Q

What is a mass spectrometer?

A

an instrument which can be used to determine the accurate formula mass of organic compounds

5
Q

What does the height of the lines in a mass spectrum represent?

A

the abundance of ions of a particular mass/charge ratio

6
Q

What does the peak with the highest m/z ratio provide?

A

the molecular mass

7
Q

What is the case with molecular ions formed by the collision of a molecule?

A

the molecules formed can either be stable enough to remain intact during their progress through the mass spectrometer or will have sufficient energy imparted by the collision to break specific bonds and produce a pattern of fragment ions at the detector

8
Q

What does a mass spectrometer do?

A

it automatically compares the mass spectrum of a compound against a database of compounds to allow identification

9
Q

Why is infrared spectroscopy used?

A

to identify functional groups and structural features in an organic compound

10
Q

What does infrared spectroscopy cause?

A

the bonds to stretch and vibrate

11
Q

What can be said about the frequency of the vibration produced by infrared spectroscopy?

A

it is dependent on the mass of the atoms and the strength of bond

12
Q

What happens as the mass increases?

A

the vibration decreases

13
Q

Summary of radiation and molecules

A

The wavelength of light absorbed that results in the different vibrations will depend on the type of chemical bond and the group of atoms at the end of these bonds

14
Q

When is infrared spectroscopy used?

A

in forensics, polymers chemistry and quality control

15
Q

What does NMR stand for?

A

Nuclear magnetic resonance

16
Q

What can NMR be used to tell us?

A
  • the different chemical environments of protons (hydrogen) atoms in a molecule
  • how many different protons (hydrogens) are in each of these environments
17
Q

What is the chemical shift?

A

The signal from any given proton is measured in ppm from TMS and is called the chemical shift of the proton and is given the symbol delta

18
Q

What are high-resolution NMR run using?

A

higher frequencies and more powerful magnets

19
Q

How can the number of lines within a multiplet be determined?

A

by looking at the number of H-atoms on the neighbouring carbon

20
Q

What is the number of peaks in a multiplet given by?

A

the n+1 rule

21
Q

What causes the separation of ions in a mass spectrometer?

A

A magnetic field

22
Q

In which technique would a test sample be destroyed?

A

X-ray crystallography

23
Q

What can be said about electron spins when there is no magnetic field?

A

The spins are random

24
Q

What happens in an nmr spectroscopy when there is a magnetic field?

A

The nuclei position themselves in alignment with the magnetic field

25
Q

What is the difference when the electrons are alinged with the magnetic field or against the magnetic field?

A

There is an energy difference

26
Q

What is the energy difference equal to?

A

The energy of the radiowaves

27
Q

What is the energy dependant on?

A

The environment of the protons

28
Q

What can be said about solvents used for NMR?

A

They must not contain any hydrogen