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Environmental Chemistry Complete Notes..

Environmental Chemistry Environmental chemistry: It is the branch of chemistry that deals with the study of various chemical processes taking place in the various segments of the environment. Broadly speaking, it is the study of the sources, transportation, reactions, effects and the ultimate of the chemical species occurring in one or more segments of the environment. Components of Environment : Atmosphere:   This comprises a blanket of gaseous layer around earth. Hydrosphere :  This comprises about 96% of earth’s surface & includes all   sources of water like oceans rivers lakes, glaciers, ground water etc. Lithosphere :  It refers to earth’s solid crust containing the outer mineral cover. It comprises soil, minerals, organic matter etc.  Biosphere:   It refers to the domain of living organism in covalent with atmosphere hydrosphere as well as lithosphere.    Environmental pollution...
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Infrared Spectroscopy

A technique called infrared (IR) spectroscopy is valuable in the study of organic compounds. This technique allows researchers to determine the kinds of bonds and functional groups that are present in a molecule. 


Using a more advanced analysis, researchers are even able to determine other groups and bonds that are nearby. This information, paired with the molecular formula of a compound, helps researchers puzzle out the precise structure of an unknown molecule.

An infrared spectrometer works by shining infrared light through a sample of a compound. Organic molecules absorb light at certain frequencies in the range of 450 nm to 4000 nm.
A sensor on the other side of the sample detects the amount of light that is absorbed by the sample at each wavelength.

When a molecule absorbs light at a certain frequency, it means that a specific bond is stretching, bending, or vibrating. The frequency where each bond absorbs light energy to stretch, bend, or vibrate is very specific. The absorption results in a decrease in intensity of the light transmitted, as measured by the sensor.

This is how an infrared spectrum is formed for a molecule. The spectrum is as specific to a certain molecule as your fingerprint is to you. The table below shows some typical locations for peaks on an infrared spectrum.


Bond or functional group
Wavelength (μm)
O-H
2.8–3.1
N-H
2.9–3.0
C-H
3.4–3.5
carboxylic acid group
2.8–4.0 and 5.8–5.9
Aldehyde
3.4–3.7 and 5.7–5.8
Ketone
5.8–5.9
Ester
5.7–5.8 and 7.7–8.5
Alkene
5.9–6.2
Alkyne
4.5–4.8
Halo alkane
13.4–20


By:-
Anjani Kumar Singh.

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