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Transcript of Chem 125 Lecture 5 9/15/06 Projected material This material is for the exclusive use of Chem 125...
Chem 125 Lecture 59/15/06
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.
Some Resonance Structures for H, C, N, O Isomers
For quantum-calculatedlocal-minimum-energyatomic arrangements
H, C, N, O isomersC in middle
H
C NO :: :
H
C NO:: :
H
C NO::
:
+
_H
C NO :: :
+ _
charge separation charge separation
H
C N O:
:
:
:H C N O:
::
+ _
:H C N O:
: +_
+_ H
C N O::
:
:
+_ H
C N O:
:
:bad charge
sestet
sestet
bad charge
bad charge
H, C, N, O isomersN in middle
H
C NO ::
:: +
_H
C NO
:
::
:
_
+
H
C NO
:
::
:
_
+
H
C NO
:
:
:
:+
_
sestet
sestet
bad charge bad charge
sestet
sestet
H, C, N, O isomersO in middle
HC
N
O
:
:
: H
CN
O: :
+: _
H
CN
O: ::
:sestet
bad charge
H, C, N, O isomerscyclic
H
C
N
O:
:
:
+ _
sestet
H
C
N
O
:
:
:
+
_
:bad charge
Can’t even be calculated(opens up)
HNCOisomers
HC
N
O
:
:
:
H
C NO :: :
H
C NO:: :
H
C N O::
::
H C N O:
::
+ _
H
C NO ::
:
: +_
H
C NO
:
::
:
_
+
H
CN
O: :
+
: _
HNCOisomers
QuickTime™ and aTIFF (LZW) decompressor
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150
100
50
0
200kc
al/m
ole
H
C N O
H
C NO
H
C NO
H C N O
H
CN
O
H
C NO
H
C NO
HC
N
O
Eca
lc
References:
Most of these structures and energies were calculated at a very high level of theory as reported in Journal of Chemical Physics, 120, 11586-11599 (2004).
The much less stable structures with O in the middle were calculated using the highest level of theory available in the Spartan 04 package of quantum programs. This program could not find an energy minimum for the cyclic structure with H on oxygen.
"[We can] solve the special case where the corpuscles are
confined to a plane."
Thomson's Model of Electron Configuration
"consider the problem as to how 1…2…3…n corpuscles would arrange themselves if placed in a sphere filled with positive electricity of uniform density…"
“distributed in the way most amenable to
mathematical calculation”
in
"[We can] solve the special case where the corpuscles are
confined to a plane."
Thomson's Model of Electron Configuration
"consider the problem as to how 1…2…3…n corpuscles would arrange themselves if placed in a sphere filled with positive electricity of uniform density…"
"the equilibrium of eight corpuscles at the corners of a cube is unstable."
in
"I have ever since regarded [the cubic octet]as representing essentially the arrangement
of electrons in the atom"
G. N. Lewis (1923)
Was Lewis ignorant ofEarnshaw's Theorem?
Conclusion of
Valence and the Structure of Atoms and Molecules G. N. Lewis (1923)
"if we use the electron as a test charge to determine the properties of the simplest possible electric field,
namely, the field about a hydrogen nucleus, we appear to find that this field is not a continuum
but is strikingly discontinuous."
The Future of the Quantum TheoryThe Discontinuity of Physico-Chemical Processes
The Electron in Chemistry
J. J. Thomson (1923)
… if [electron-nuclear attraction] were to vary strictly as the inverse square of the distance we know by Earnshaw's theorem than no stable configuration in which the electrons are at rest or oscillating about positions of equilibrium is possible ...
… then a number of electrons can be in equilibrium about a positive charge without necessarily describing orbits around it.
I shall assume that the law of force between a positive charge and an electron is expressed by the equation
F =Eer2 1−
cr
⎛ ⎝
⎞ ⎠
cr
atomic length scaleCouloumb
Quantum Mechanics (1926)
kinetic energy reformulated to explain electron clouds and produce an "inverted"
plum-pudding atom.
Cubic octets and ad hoc force lawssoon disappeared from conventional
Chemistry and Physics
But shared-pairs and lone-pairsremained useful tools for discussing
structure and bonding.
OCCULT CHEMISTRY
A SERIES OF
Clairvoyant Observations on theChemical Elements
BY
ANNIE BESANT, P.T.S.
AND
CHARLES W. LEADBEATER
Reprinted from the Theosophist.
THEOSOPHIST OFFICE, ADYAR, MADRAS, S.
THEOSOPHICAL PUBLISHING SOCIETY, LONDON AND BENARES CITY.
1909 (105 pp.)
1919 (123 pp.)
1951 (400 pp.)
Mrs. AnnieBESANT
P.T.S.(1847-1933)
CuruppumullageJINARAJADASA
P.T.S.(~1877-1953)
"Bishop"Charles WebsterLEADBEATER
(1847 - 1932)
The Occult Chemists (1895-1932)
4forbital
e-density
Occult Atoms
Bases for Belief:
1) Evidence "cross-examine an assertion"
2) Taste matures with experience
Na2CO3(1924)
"note that this trian-gular arrangement of O3 has just been deduced by Bragg from his X-ray analysis of Calcite"
Benzene(1924)
"each of the three valencies of each Carbon are satisfied by Hydrogen, and the fourth valency, which some have postulated as going to the interior of the molecule, does actually do so."
Cf. Wiki: Question 6
“Credit” for use?
1 cm3 of water ≈
1024 molecules
€
10243 =108
molecules / cm
Are Molecules Unobservably Small for
"Vulgar" Eyes?
105
Lecture Room ~10 m
Hair ~100 m
Nucleus ~10 fm
Molecule ~1 nm(small atom ~ 0.1 nm = 1 Å)
101
10-4
105
10-9
105
10-14
105
Query 31
…the Attraction [between glass plates separated by a thin film of Oil of Oranges] may be proportionally greater, and continue to increase until the thickness do not exceed that of a single Particle of the Oil.
p. 175
Newton Opticks (1717)
= cos-1(0.29"/(12"51')) = 89.973°
air gap
0.29"
= (1251)(1-sin ) = 7 10-5 inch = 1.8 m
51'