Imines (nitrogen analogues of carbonyl compounds) are formed when any primary amine reacts with aldehyde or ketone under appropriate conditions. Mechanically, the amine first attacks the aldehyde with formation of an intermediate. Its subsequent dehydration gives the imine. Imine formation is like a biological reaction: it is fastest near neutrality. Many biological processes involve imine formation. Three outstanding examples are: synthesis of amino acids from oxoacids, transamination of acids and mechanism of vision. The former two α-amino processes include formation of an imino intermediate between an amino acid and vitamin B6 derivative (pyridoxal). The transformation of light energy into electric signal in our eyes includes the of a polyene retinal (an aldehyde), which is covalently linked to cis-trans-photoisomerization the protein (an amine) by the imine bond. Imines are also very important in organic synthesis as intermediates in the so-called reaction allowing direct transformation of “reductive amination” carbonyl compounds into amines. In this task you will prepare aniline derivative of benzaldehyde (I). Chemicals and Reagents Aniline Benzaldehyde 96% aqueous ethanol Table of Chemicals Compound State R-Ratings S-Provisions 23/24/25 40 41 43 26 27 36/37/39 45 C6H7N, Aniline Liquid 48/23/24/25 50 68 46 61 C7H6O,Benzaldehyde Liquid 22 2 24 C2H6O, Ethanol, 96% Liquid 11 2 7 16 aqueous solution Equipment and Glassware Magnetic stirrer with heating Magnetic bar Glass beaker, 25 mL Round-bottom two necked flask, 50 mL Reflux condenser Laboratory stand with metal rings and clamps Adding funnel Separating funnel Filter flask glass filter Porous Shott’s Water- or vacuum pump
Imines (nitrogen analogues of carbonyl compounds) are formed when any primary amine reacts with aldehyde or ketone under appropriate conditions. Mechanically, the amine first attacks the aldehyde with formation of an intermediate. Its subsequent dehydration gives the imine. Imine formation is like a biological reaction: it is fastest near neutrality. Many biological processes involve imine formation. Three outstanding examples are: synthesis of amino acids from oxoacids, transamination of α-amino acids and mechanism of vision. The former two processes include formation of an imino intermediate between an amino acid and vitamin B6 derivative (pyridoxal). The transformation of light energy into electric signal in our eyes includes the cis-trans-photoisomerization of a polyene retinal (an aldehyde), which is covalently linked to the protein (an amine) by the imine bond. Imines are also very important in organic synthesis as intermediates in the so-called “reductive amination” reaction allowing direct transformation of carbonyl compounds into amines. In this task you will prepare aniline derivative of benzaldehyde (I). Chemicals and Reagents Aniline Benzaldehyde 96% aqueous ethanol Table of Chemicals Compound State R-Ratings S-Provisions C6H7N, Aniline Liquid 23/24/25 40 41 43 48/23/24/25 50 68 26 27 36/37/39 45 46 61 C7H6O,Benzaldehyde Liquid 22 2 24 C2H6O, Ethanol, 96% aqueous solution Liquid 11 2 7 16 Equipment and Glassware Magnetic stirrer with heating Magnetic bar Glass beaker, 25 mL Round-bottom two necked flask, 50 mL Reflux condenser Laboratory stand with metal rings and clamps Adding funnel Separating funnel Filter flask Porous Shott’s glass filter Water- or vacuum pump
Preparatory_problems_IChO_2013.docx