LI: To understand the purposes of spectroscopy. To understand what is required in AS 3.3 - Spectroscopic Data - 3 credits internal

Spectroscopy is a process used to analyse unknown substances are present in a sample In today's world chemicals are analysed daily by simple test strips or machines to detect the presence of particular drugs or analyse medical compounds

Police and airport security and sports organisers use these tests routinely to identify certain banned chemicals they are testing for. It is much harder however to view an unknown sample and analyse what is there if it is not a known substance. Researchers in their search for cures for diseases or scientists looking to synthesise new compounds need to be able to SEE the structure of molecules.

If atoms are so tiny how do we know what molecules look like? This is question often asked in Junior Science.... The Light of Knowledge is an often used phrase, but it is particularly appropriate in reference to spectroscopy. Most of what we know about the structure of atoms and molecules comes from studying their interaction with light (electromagnetic radiation). Different regions of the electromagnetic spectrum provide different kinds of information as a result of such interactions.

The electromagnetic spectrum is: Electromagnetic radiation can be described as a stream of photons, each traveling in a wave-like pattern, carrying energy and moving at the speed of light. The main difference between radio waves, visible light and gamma rays is the energy of the photons. Radio waves have photons with the lowest energies whereas gamma rays have photons with the highest energies. The electromagnetic spectrum is:

Seeing Molecules... In order to "see" a molecule, we must use light having a wavelength smaller than the molecule itself (roughly 1 to 15 angstrom units). Such radiation is found in the X-ray region of the spectrum, and the field of X-ray crystallography yields remarkably detailed pictures of molecular structures amenable to examination. The chief limiting factor here is the need for high quality crystals of the compound being studied. .

this method but 3 other forms of spectroscopy... In this A.S. we don't use this method but 3 other forms of spectroscopy... Mass spectrometry - to analyse the molecular weight of a molecule in the sample (Mr) Infrared spectroscopy - to analyse the functional groups found on the molecule 3. NMR spectroscopy - to analyse how many carbon "areas" the molecule has.

1. Mass Spectrometry: Sample molecules are ionized by high energy electrons. The mass to charge ratio of these ions is measured very accurately by electrostatic acceleration and magnetic field perturbation, providing a precise molecular weight. Ion fragmentation patterns may be related to the structure of the molecular ion. (Not strictly spectroscopy as doesn't use Electromganetic spectrum)

Mass spectrometry

2. Infrared Spectroscopy: Absorption of this lower energy radiation causes vibrational and rotational excitation of groups of atoms within the molecule. Because of their characteristic absorptions identification of functional groups is easily accomplished.

IR (Infrared) Spectroscopy

3. Nuclear Magnetic Resonance Spectroscopy Absorption in the low-energy radio- frequency part of the spectrum causes excitation of nuclear spin states. NMR spectrometers are tuned to certain nuclei (e.g. 1H, 13C, 19F & 31P). For a given type of nucleus, high- resolution spectroscopy distinguishes and counts atoms in different locations in the molecule (different carbon areas)

NMR spectroscopy

Your task... Using the clues provided in 3 spectrum and some other written clues you are to identify the structure of an organic molecule containing some of the functional groups and structures we have studied so far this year... Written assessment with all info tables provided. 3 credits - 1 hour test. Easy!