Classify organic dyes according to their chemical composition.
Colouring materials have been used for many thousands of years by man. Leather, cloth, food, pottery and housing have all been modified in this way. The two old ways were to cover with a pigment (painting), or to colour the whole mass (dyeing). Pigments for painting were usually made from ground up coloured rocks and minerals, and the dyes were obtained from animals and plants. Today, many of the traditional dye sources are rarely, if ever, used (onion skins, for instance). However, some of our most common dyes are still derived from natural sources. These are termed natural dyes. The Colour Index uses this as a classification and naming system. Each dye is named according to the pattern:
–Natural + base colour + number
These dyes are thereby specifically identified as dyes of the stated colour, and which may still be derived from animals or plants. Note that this is a classification based on the dye’s source and colour. It contains no chemical information; neither does it imply
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How would you prepare cis and trans alkene from alkyne? Give its mechanism.
Complete following reactions:
Write the product and indicate the type of reaction that is taking place in the following:
Explain the following:
i) E2 elimination does not give rearranged product.
ii) E1 elimination does not involve isotope effect;
iii) Hofmann elimination gives less substituted alkene
iv) An anti elimination is faster than syn-elimination.
v) The elimination of HCl from chlorofumaric acid is 50 times faster than
chloromalic acid.
In Wittig reaction, the methyl, primary and secondary alkyl halide can be used to
prepare Wittig reagent (ylide) but not tertiary alkyl halide.
Draw and explain potential energy diagram for the reaction of addition of HCl to 1, 3- butadiene at a low and high temperatures.
Aromatic aldehydes are less reactive than aliphatic aldehyde.