Chem 125 Lecture 10/30/02 Projected 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 Why do gases of different density remain mixed rather than stratifying? amateur meteorologist 1801 Continental Europeans proposed hetero-attraction, but Dalton preferred Newtonian repulsion.

"the atoms of one kind did not repel the atoms of another kind" Atom Heat Envelope substitutes homorepulsion for heteroattraction

Berzelius Analysis (1) Tube 1/2” diameter (Fig 1) charged with dried powder containing ~0.5 g of organic substance, 3 g NaClO 3 (O 2 source), 50 g NaCl. (2) Neck of tube heated and drawn out (Fig 2) (3) Joined (Fig 4) to water collecting bulb (Fig 3) and CaCl 2 drying tube with rubber tubing (4) Assembled (Fig 6) so that gas (O 2, CO 2 ) that exits drying tube bubbles into bell-jar containing Hg with floating bulb (Fig 5) holding KOH (to absorb CO 2 ) and closed with permeable glove leather to keep out Hg. Wire attached to bottom so bulb can be retrieved from bell-jar.

(6) To be certain the KOH absorbs all of the CO 2 through the glove leather, wait 12 hours after the mercury stops rising in the bell jar before disassembling and weighing. 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.

Based on O = 100 or H 2 = 1 Bars denote doubled atoms O = [15.999] (-1.0%) (-1.0) (0.4) (1.3)

Friedrich Wöhler ( ) 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.”

Liebig 1836 Justus Liebig ( )

SCL

Kaliapparat

Liebig Analysis (1831) H 2 O Collector Combustion CO 2 Collector

Lab Liebig’s Laboratory in Giessen

Lab Workers

Stammbaum Liebig’s Scientific Descendents Red = Nobel Prize

What Can You Show With Analysis? Oil of Bitter Almonds C7H6O2C7H6O2 O2O2 C 7 H 5 OCl Cl 2 Liebig & Wöhler (1832) C7H6OC7H6O C 7 H 5 OBr Br 2 C 7 H 5 OI KI C 7 H 7 ON NH 3 C 14 H 10 O 2 S PbS So? Persistence of C 7 H 5 O Benzoyl Radical Bz H Bz OH Bz Cl Bz Br Bz I Bz NH 2 Bz 2 S Dualism /

During the 1830s compound radicals were discovered everywhere: Liebig: Acetyl Ethyl (Berzelius) Bunsen: Cacodyl (Me 2 As ) Piria: Salicyl Dumas: Methyl Cetyl Cinnamyl Ethylene

C 2 H 3 O OHC 2 H 2 ClO OH By 1840 photochlorination of acetic acid had transmuted the acetyl "element". ClH Cl +=+ C 2 H 3 O OHC 2 H 2 ClO OH Trouble in Paradise C 7 H 5 O HC 7 H 5 O ClClH Cl +=+ C 7 H 5 O Cl + - H Cl + - The electronic character of radicals was troublesome for dualism. ++ C 7 H 5 O H ?