Chem 125 Lecture10/30/02Projected material This material is for the exclusive use of Chem 125 students at Yale and may not be copied or distributed further. It is not readily understood without reference to notes from the lecture.
John Dalton amateur meteorologist 1801 Why do gases of different density remain mixed rather than stratifying? Continental Europeans proposed hetero-attraction, but Dalton preferred Newtonian repulsion.
Atom Heat Envelope substitutes homorepulsion for heteroattraction "the atoms of one kind did not repel the atoms of another kind"
(4) Assembled (Fig 6) so that gas (O2, CO2) that exits drying tube bubbles into bell-jar containing Hg with floating bulb (Fig 5) holding KOH (to absorb CO2) and closed with permeable glove leather to keep out Hg. (1) Tube 1/2” diameter (Fig 1) charged with dried powder containing ~0.5 g of organic substance, 3 g NaClO3 (O2 source), 50 g NaCl. (3) Joined (Fig 4) to water collecting bulb (Fig 3) and CaCl2 drying tube with rubber tubing (2) Neck of tube heated and drawn out (Fig 2) Wire attached to bottom so bulb can be retrieved from bell-jar. Berzelius Analysis
(5) Build fire in brick enclosure to heat tube slowly from near end to far. Tube wrapped with metal sheet to keep it from popping under pressure necessary to bubble through Hg when it softens at red heat. Berzelius Analysis (6) To be certain the KOH absorbs all of the CO2 through the glove leather, wait 12 hoursafter the mercury stops rising in the bell jar before disassembling and weighing.
O = 15.9994 [15.999] 0.998 (-1.0%) Bars denote doubled atoms 14.162 (-1.0) 32.185 (0.4) 30.974 (1.3) Based on O = 100 or H2 = 1
Letter to Berzelius (1837) “To see this old friend [Palmstedt] again, especially here [in Göttingen], was a real delight. He was just the same old guy, with the sole exception that he no longer wears the little toupee swept up over his forehead as he used to.” Friedrich Wöhler(1800-1882)
Liebig 1836 Justus Liebig (1803-1873)
CO2 Collector Liebig Analysis (1831) Combustion H2O Collector
Lab Liebig’s Laboratory in Giessen
Stammbaum Liebig’s Scientific Descendents Red = Nobel Prize
Persistence of C7H5O So? Dualism / Benzoyl Radical C7H5OI C7H6O2 O2 Bz • I Bz • OH KI NH3 Cl2 C7H7ON C7H5OCl Bz • NH2 Bz • H Bz • Cl Br2 PbS C14H10O2S C7H5OBr Bz2• S Bz • Br What Can You Show With Analysis? Liebig & Wöhler (1832) Oil of Bitter Almonds C7H6O
Piria:Salicyl Dumas:Methyl Cetyl Cinnamyl Ethylene During the 1830s compound radicals were discovered everywhere: Liebig:AcetylEthyl(Berzelius) Bunsen:Cacodyl(Me2As•)
C7H5O • H + = + C7H5O • H Cl C7H5O • Cl H • Cl C7H5O • Cl H • Cl + + - - + + ? By 1840 photochlorination of acetic acid had transmuted the acetyl "element". + = + C2H3O • OH C2H3O • OH Cl C2H2ClO • OH C2H2ClO • OH H • Cl Trouble in Paradise The electronic character of radicals was troublesome for dualism.