Chem 125 Lecture10/30/02

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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.”

Liebig 1836JustusLiebig(1803-1873)

SCL

Kaliapparat

Liebig Analysis (1831)

H2OCollector

Combustion

CO2 Collector

Lab

Liebig’s Laboratory in Giessen

Lab Workers

Stammbaum

Liebig’s Scientific Descendents

Red = Nobel Prize

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

C2H3O • OH C2H2ClO • OH

By 1840 photochlorination of acetic acidhad transmuted the acetyl "element".

Cl H • Cl+ = +C2H3O • OH C2H2ClO • OH

Trouble in Paradise

C7H5O • H C7H5O • ClCl H • Cl+ = +C7H5O • Cl+ -

H • Cl+ -

The electronic character of radicalswas troublesome for dualism.

++C7H5O • H

?