The main modes of vibrations are stretching and

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The main modes of vibrations are stretching and bending vibrations. Stretching vibrations case a bond length increase or decrease at regular intervals. Stretching vibrations are divided in symmetrical and asymmetrical stretching. In the symmetrical stretching bond length decrease or increase symmetrical and in the asymmetrical stretching length of only one bond increases and the other one decreases. Bending vibrations are when bond angle change between bonds with a common atom or if there is a movement of a group atoms with respect to the reminder of the still molecule of the atoms in the group with respect to each other. Bending vibrations also known as deformations are divided into 2 types which are In plane and out of plane bending vibrations. In plane bending vibrations are Scissoring in which bond angles decreases and Rocking where the bond angle is maintained but both bonds move within the same plane. Out of plane bending, wagging occurs which is when both atoms move to one side of the plane and it takes place outside of the plan of molecule. Infrared spectroscopy is used to identify unknown materials, it helps to find out what components are in the mixture and their amount and also it shows quality of the sample. The fingerprint region is places on the right hand side of an infrared spectrum and this region is below 1500 to 500 cm -1 . It can be used to compare 2 similar compounds. A small difference in the structure and constitution of a molecule results significant changes in the absorption
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bands. Also in this region compounds will show their unique absorption bands which helps for the identification of the compound. It can show us if we had an alcohol because when identifying compounds there would tell us that there is OH group presented in our blood. Then the infrared region would be compared with with measured spectra to find out what alcohol is presented in our blood.
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