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For example, benzene does not display colour as it does not have a chromophore; but nitrobenzene is pale yellow colour because of the presence of a nitro group (−NO 2) which acts as a chromophore. But p-hydroxynitrobenzene exhibits a deep yellow colour, in which the −OH group acts as an auxochrome.
A chromophore is a molecule which absorbs light at a particular wavelength and reflects color as a result. Chromophores are commonly referred to as colored molecules for this reason. The word is derived from Ancient Greek χρῶμᾰ (chroma) 'color' and -φόρος (phoros) 'carrier of'.
Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline.
Most modern synthetic dye molecules contain two components. The first part is an aromatic benzene ring or system of benzene rings, often substituted. The second is a chromophore, a conjugated double bond system with unsaturated groups. When exposed to visible light, this part absorbs or reflects color.
Inputs used in the calculation are the type of chromophores present, the auxochromes (substituents on the chromophores, and solvent. [ 1 ] [ 2 ] Examples are conjugated carbonyl compounds, [ 3 ] [ 4 ] [ 5 ] conjugated dienes , [ 3 ] [ 6 ] and polyenes .
It can be considered as next in the series of benzene, biphenyl, para-terphenyl. It is an aromatic hydrocarbon and a chromophore. One possible use is in scintillation counters where it is dissolved in toluene and glows when subject to beta rays. [1]
Cinnamaldehyde is a naturally-occurring compound that has a conjugated system penta-1,3-diene is a molecule with a conjugated system Diazomethane conjugated pi-system. In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability.
Benzene has three aromatic π → π* transitions; two E-bands at 180 and 200 nm and one B-band at 255 nm with extinction coefficients respectively 60,000, 8,000 and 215. These absorptions are not narrow bands but are generally broad because the electronic transitions are superimposed on the other molecular energy states .