CHEM 222 Lecture Notes - Lecture 1: Infrared Spectroscopy, Molecular Vibration, Chemical Formula
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Chapter 1: 1, 3, 5, 7, 9, 11. How to obtain an empirical formula from elemental analysis data: Step 1: divide the weight percentage by the atomic mass to determine the molar ratio: 63. 04 %c/12. 01 = 5. 26, 7. 98 %h/1. 008 = 7. 92, 18. 45 %n/14. 01 = 1. 32 10. 58 %o/16. 00 = 0. 66. Step 2: divide the values in the ratio by the smallest value. C: 5. 26/0. 66 = 7. 97 8 h: 7. 92/0. 66 = 12. 00 n: 1. 32/0. 66 = 2. 00 o: 0. 66/0. 66 = 1. 00. Step 1: reduce the molecular formula to the formula of a hydrocarbon (cnhm) with the same degree of unsaturation. Replace all halogens (f, cl, br, i) in the molecular formula by hydrogens. For each nitrogen, omit the nitrogen and delete one hydrogen. U = (2n + 2) m = n m/2 +1. When u is greater than or equal to 4, this strongly suggests the possibility of an aromatic (eg. benzene ring . 1 ring, 3 pi bonds u = 4)
