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Inorgnic and Analytical Chemistry
Dr. Muhammad Afzal SubhaniSchool of Chemical & Materials EngineeringNUST H-12 Islamabad
Course CHEM-101
Mass, NMR and IR Spectroscopy
IR Spectroscopy
Principles
• Absorption of electromagnetic radiation in the infrared region of the spectrum resulting in changes in the vibrational energy of molecules.
Instrumentation
• IR spectrometer or double-beam spectrophotometer
• incorporating prism or grating monochromator,
• thermal or photon detector,
• alkali halide cells.
Applications
• largely for the identification and structural analysis of organic materials
• Near infrared region used increasingly for industrial quality control.
Disadvantages
• Difficult to analyse mixtures. Special cells required for aqueous samples.
IR Spectroscopy
IR Spectrophotometer
IR Spectroscopy
The first question that which bond will vibrate?
• much stronger or weaker than others nearby
or• between atoms that are much heavier
or lighter than their neighbours• The relationship between frequency of
the bond vibration, the mass of the atoms, and thestrength of the bond is described by equation 1
• Where;
– f is force constant more or less bond strength
– μ is Reduced mass which is given by equation 2
equation 1 equation 2
IR Spectroscopy
What Kind of IR spectra is?
IR Spectroscopy
Kind of Vibrations
X—H Vibrations
Saturated and unsaturated groups
IR Spectroscopy
IR Spectroscopy
IR Spectroscopy
The X–H IR stretches are very different in these four compounds.
Mass spectrometry
Mass spectrometry
Introduction
• It gives information about molecular weight and composition of a compound
Instrumentation
• A source to volatilize and ionize the molecule into a beam of charged particles
• something to focus the beam so that particles of the same mass:charge ratio are separated from all others
• A detector to detect the particles
• All spectrometers in common use operate in a high vacuum
Mass spectrometry
Mass spectrometry
Mass spectrometry by electron impact
Mass spectrometry
