chem 125 lecture 10/30/02 projected material this material is for the exclusive use of chem 125...
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Chem 125 Lecture10/30/02
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
HeatEnvelope
substituteshomorepulsion
for heteroattraction
Berzelius Analysis
(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.(2) Neck of tube heated and drawn out (Fig 2) (3) Joined (Fig 4) to water collecting bulb (Fig 3)
and CaCl2 drying tube with rubber tubing
(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. Wire attached to bottom so bulb can be retrieved from bell-jar.
(6) To be certain the KOH absorbs all of the CO2 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 H2 = 1
Bars denotedoubled atoms
O = 15.9994
[15.999]
0.998 (-1.0%)
14.162 (-1.0)
32.185 (0.4)
30.974 (1.3)
Friedrich Wöhler(1800-1882)
Letter to Berzelius (1837)
“To see this old friend [Palmstedt] again, especiallyhere [in Göttingen], was a real delight. He was just the same old guy, with the sole exception that he no longerwears the littletoupee swept up over hisforehead ashe used to.”
What Can You Show With Analysis?
Oil ofBitter
Almonds
C7H6O2O2
C7H5OClCl2
Liebig & Wöhler (1832)
C7H6O
C7H5OBr
Br2
C7H5OIKI
C7H7ONNH3
C14H10O2S
PbS
So?Persistence of C7H5O Benzoyl Radical
Bz • H
Bz • OH
Bz • Cl
Bz • Br
Bz • I
Bz • NH2
Bz2 • S
Dualism /
During the 1830s compound radicals were discovered everywhere:
Liebig: Acetyl Ethyl (Berzelius)
Bunsen: Cacodyl (Me2As •)
Piria: Salicyl
Dumas: Methyl Cetyl Cinnamyl Ethylene
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