(1) The structure of brominated tetrachlorophenol para-phenol. In the past, it was considered that it has three possible structures, but it has not been identified and confirmed. It has been confirmed by infrared spectroscopy that there is only one structure.
(2) Dimolecular aldehyde condensed alcohol ketone, which should be of formula (I). If the formula (I) is replaced by a pyridyl group, the chemical property and (I) are different, and it has an olefinic diol type reaction such as the formula (II). However, in the solution of the polarene, the 3700 cm (-1)-band of the free hydroxyl group was not observed, but the all-hydrogen bond appeared at 2750 cm (-1). It is known that it has formed intramolecular hydrogen bonds.
(I) hydroxyketone (II) olefinic diol
2. Determination of isomers - can identify stereoisomers and isomers
(1) Determination of cis-trans isomers - The order of the cis-trans isomer groups is due to the absence of a symmetry center, so the C=C double bond is at 1630 cm (-1), 724 cm (-1), and the trans C=C Higher frequency.
(2) Identification of isomers - In the infrared spectrum, the aliquots with different positions of benzene ring substitution can be seen in the 900-660 cm (-1) region. The absorption bands of the three isomers such as xylene are quite different. The ortho position is 742cm (-1), the meta position is 770cm (-1), the para position is 800cm (-1), and because of the strong symmetry of para-xylene, its C=C double bond (benzene skeleton) is 1500cm ( -1) becomes smaller, and the 600 cm (-1) band disappears. Vortex flowmeter
Another example is n-propyl, isopropyl, tert-butyl as seen by the methyl bending vibration in the infrared spectrum. When only one absorption band appears at 1375 cm (-1), it is expressed as n-propyl; if a double peak of equal intensity appears at 1375 cm (-1), it is isopropyl; if it is at `1390 cm (-1) and 1365 cm ( -1) A strong-weak band appears as a tert-butyl group.
The molecular formula of ethanol and methyl ether is exactly the same as C2H6O. The hydroxyl absorption band of ethanol is 3500cm(-1), the stretching vibration of C-0 is 1050~1250cm(-1), and the bending vibration of hydroxyl is 950cm(-1). Methyl ether has no hydroxyl absorption at 3500 cm (-1). Its * strong 1150 ~ 1250cm (-1), these two isomers are easy to distinguish.
3. Inspection of chemical reactions - whether a chemical reaction has been carried out completely, can be checked by infrared spectroscopy, because the raw materials and expected products have their characteristic absorption bands.
For example, when the secondary alcohol is a ketone, the hydroxyl absorption of the secondary alcohol of the raw material should disappear, and the carbonyl group 171 cm (-1) of the ketone should appear in the product before the reaction proceeds to completion.
4. Analysis of unknowns - The unknowns can be separated and purified, elemental analysis, molecular formula, and unsaturation calculated. From the infrared spectrum, information on the main functional group of the unknown can be obtained to determine which compound it belongs to. The structure of this compound can be identified by combining ultraviolet, nuclear magnetic or the like.
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