Experimental determination of structure, pharmaceutical chemistry Flashcards
What can elemental microanalysis (/combustion analysis) be used to determine
Empirical formula of an organic compound
Describe the process of elemental microanalysis
A tiny sample is accurately weighed and oxidised at a high temperature in an oxygen rich atmosphere
The product mixture of CO2, H2O, N2, SO2 is separated using gas chromatography and the mass of each component is measured using a thermal conductivity detector
What is mass spectrometry used for
A technique to determine the accurate molecular mass and structural features of a compound
What happens to the sample being analysed in a mass spectrometer
It is vaporised and and bombarded with high energy electrons which knocks electrons off the molecule and as a result the molecules break into positively charged ion fragments
What happens to the positively charged ion fragments in a mass spectrometer
They’re accelerated by a high voltage electric field into a strong magnetic field that deflects them into a series of separate ion paths according to their mass/charge ratio.
What is the difference between positive ion fragments with a lower or higher mass/charge ratio
Ions with lower mass/charge ratios are deflected more than those with higher ratios
What are the common types of bond vibration
Stretching and bending
What affect does infrared radiation have on bonds
Causes them to vibrate but not break
What determines the wavelenght of infrared radiation that a bond absorbs
The type of atoms and the stiffness (strength) of the bond
In general, which bonds absorb infrared radiation with a shorter wavelength
Light atoms with stiff bonds
What does infrared spectroscopy make use of
Identifies the atoms and bond strength of a bond to identify specific bonds and functional groups
Describe the process of infrared spectroscopy
Infrared radiation is passed through the sample in a spectrometer, Some wavelengths are absorbed causing bonds to vibrate.
The transmitted radiation passes to a detector where the intensity of different wavelengths is measured.
Explain why protons behave like tiny magnets when placed between the poles of a powerful magnet
Some atomic nuclei spin about their own axes
Whats the energy of protons aligned with the magnetic field compared to those aligned against it
Protons aligned with the field have lower energy
What corresponds to the radio frequency region of the electromagnetic spectrum with reference to proton nuclear magnetic resonances spectroscopy
The energy difference between protons aligned with and against the magnetic field