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Meeting 8 (Condensed Key)
1. a. The 2,6-dimethylnitrobenzene is the oxidizing reagent and stannous chloride is used as the reducing reagent in the reaction. The nitrogen atom in the nitro group is reduced from its (+3) oxidation state to (-3) oxidation state, which requires six electrons per nitro group. Thus, three equivalents of SnCl2 (stannous chloride) are required per nitro group because each tin(II) is oxidized to tin(IV) in the reaction, which is a two electron step .
RNO2 + 3 SnCl2 + 7 HCl -----> RNH3+Cl- + 3 SnCl4 + 2 H2O (R=2,6-(CH3)2C6H3)
b. Glacial acetic acid is used as solvent in the reaction to dissolve 2,6-dimethylnitrobenzene, which does not dissolve in the strongly ionic aqueous solution.
c. The reaction of the xylidinium salt with potassium hydroxide releases the free amine (2,6-dimethylaniline=2,6-Xylidine) in an acid-base reaction.
R-NH3+ + OH- -----> RNH2 + H2O
d. The product is a base (primary amine), which would absorb much stronger on acidic drying agents like anhydrous sodium sulfate or anhydrous magnesium sulfate. Potassium carbonate is used as drying agent because the compound displays a lower affinity towards a basic drying agent.
e. A vacuum adapter is required to provide a pressure exchange during the distillation. It is placed between the water-jacketed condenser and the receiving flask.
2. a. The procedure in the reader asks to use 1.1 equivalents of the acyl chloride. The given amount of 2,6-dimethylaniline is equal to 10.6 mmol (=(1.30 mL*0.9842 g/mL)/(121.18 g/mol). Thus, 11.6 mmol of the acetyl chloride should be used, which is equal to 0.92 mL (=(11.6 mmol*112.94 g/mol)/1.42 g/mL).
b. Acyl chlorides are very reactive and among other compounds also react with water to form the corresponding carboxylic acid.
ClCH2COCl + H2O ---- > ClCH2COOH + HCl
c. Sodium acetate is used as a base, which deprotonates the protonated form of the amide.
[RNH2-COCH2Cl]+ + CH3COO- -----> RNHCOCH2Cl + CH3COOH
d. The infrared spectrum of the amide displays only one N-H peak at n=3214 cm-1 and a strong carbonyl peak at n=1648 cm-1. The peaks that are due to the primary group (n=1622 cm-1 (NH2, bend), 3473cm-1 (asym. stretching), 3388 cm-1 (asym. stretching)).