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APRIL 7386

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WLee cp Th oF

Southern College Se THERES

 

FESS Pre.
gS

eS eS ames . Collegedale, Tennessee 37315
Physics Department Telephone 615-238-2111

Aprth 9, 1986

Joshua Lederberg, President
Rockefeller University

1230 York Ave.

New York, NY 10021

Dear Dr. Lederberg:

Some years ago when you were at Stanford University, you Led out in what appears
to me to be a Landmark contribution in Fundamental Chemistry. I refer to the calkeula-
tion of the number of Lsomers which a moLecule might have given its constituent atoms.
I have been able to obtain some information about the results of this work, including
the article "The Scope of Structural Tsomerism,” by Dennis H. Smith, and two articles
by L. M. Masinter® from a series on artificial intelligence.

I have a desperate need to find information on the number of possible tsomers for
as many moLecules as possible. This need exists in order to clarify an important fea-
ture 40n the nertodic system which we believe can be constructed for mokecukes with any
given number of atoms. The periodic system for diatomic molecules has been extensively
demonstrated to agree with the data and to allow the prediction of new data. Work on
the periodic system for triatomica moLecules has begun. As the number of atoms in the

molecule increase, the problem of isomers grows more and mone important - hence this
Letter.

The articles by Masinter*give the number of isomers for a few mokecules. The
article by Smith gives the number of isomers for a Large nwnber of mokecubes, but

tel af

A Liberal Arts College operated by the Seventh-day Adventist Church
Dx. Joshua Lederberg 2
Aprik 9, 1986

unfortunateky the numbers of hydrogen atoms are not Listed (the degree of unsaturation
4& Listed). TI know that, in principle, it should be possible to reconstruct the mole-
cular formula inckuding the number of hydrogens with the tabulated information. How-
ever, our time and expertise are Limited and s0 I am uniting to see whether you might
have the original print-outs in which the number of tsomers are Listed for the specific
molecules inckuding the exact number of hydrogen atoms. IT venture to take your time
for this question because of the invitation at the end of Dr. Smith's article.

Your attention to this question and any assistance you might be able to render
(such as to whom to write for the necessary information) are deeply appreciated.

Respectfully yours,

oy iis

Ray Hefferlin,
PAO feSSOA Of Physics

RH' Lh
ScoPE OF STRUCTURAL [SOMFRISM

such plots display a slightly decreasing slope with increas- Table [. Structural Isomers ot CON, O.. x ty tes 6,

ue Pele Uns. turation, b
ing carben number for each given unsaturation, for Allowed Values of she ‘

As unsaturation increases, the slopes of the curves in-
crease sharply (see Fegure 1 as U increases from zera to So. of __ Ursa: uration
four). Foweser, curves representing h higher unsaturation ane oo 1 SO ‘ .
counts frequen tly begin, and remain for a short time helow
CUTVES rese sting lower unsafuration counts, for exam-

nm
we
f
n
a

   

   

a t
: 5 , ; i 1
ple, the cu-ves fur U = 3 and U = $, Figure 1. Tt seers clear : 3 3 1
: 3 r =
that the higher the degter of unsaturation the greater the \ 3 9 7 3
pe asible number ard combinations of multiple ‘bonds and 5 10 26 40 21 6
25 v7 27 Lea fore)

w

ring sVstems, Pht factor is responsible for increasing slope

   

 

   

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1
1
1
7
3
5
1
with increasing U shesewed | in Figure 1, But, carrying this ‘9 1 1
1 \
argument to its extrer eat hy sh uld not the number of isn- O, 9 3 3 1
mers foragiven cory cation of stoms always he greater for 50, 3 9 13 9 2 7
higher un Sitipation coints, as long as the total velence of Oo, ‘ 26 °? 2 ae
ner unset en coimts, é ge ast pa we C,O, 14 74 905 335 312 14) 21
the compos't fan support the speci ified uvsatura- Co. 1 1
tion? The next section discusses thes point in mere tetoll co. 2 2 1
The Sanker of Stroctaral T.omers vs. & Trgatnration Ba? ret 5 2 ~
-" hkle - J, or ag i
Count selenite: ' data from Table I are Co 28 122 an} 182 25
combinations of six atoms. This O° } 1
. 3
cal rise and pal af the nuniber of Cc, 3 4
ic trate with inere ad Sssaturat ion, Vhe value of umsatue Cc to a 3
. . “| 25 Qe Go 6
ration a wk hi the ronvbher of isomers! C, ; fe 182 a ae
: 1 . : > . 0, 1 1
is peor tex Peaction of the number aad i it ce 5 6 2
Phe vation ctatis slowly toh He Co, WAS il 14

 

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Sane chow nasi oar Cos lor 2. Seseralen qposd
ety of six ators have moxima at Uo = 8. Hoewever,

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iss ioe te qote thar thers is a sm cath variation CN, 4
. . . i >
uf Dee atthe tiratian NG CN, l? .
.- CLN, 34 2
of isocie CoN i 1G 15
. oN, t a ! Loe
saturations Ne
uh Megatutath No 1 1
or hegrar CN, 7 4
* 7 N 7 7 3
i ane obs. Cx», 6 is -
booty re . cree CN, l4 De ‘
vera alth rhe ef ate on the nur CN, es 218 Ao t oe!
ro! ecbobane cope of ator with another type N, 1 9 1
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Nf hoa eta pret wher of CLN, 14 ; 119
— . ¢ CN, AD 2 i Lok
¢ . at t re rye 2 =
ato atayr ye Sy Ny 5 4 4
Paes a roore dis HDL CN $ a =
. + . + . . r ~! * 27 wy a 1
prone thos ds tras, as ines! han " we a: aN : : 5 :
Gare of GON Tie obewe the cueve of Co for all afl coN 1s aan we ; 12
ey -aN og , . : ™~, o pos a ber +.
theocaree of CO) les ahexve that of for OS l<4. hob N t LA 2A iS b
Peaetiabs ot that ina conmporsonaf the reautt of NS ] 1
1 an : - Noose Loe we Cc 3 a 3
rye tece te ether on N or one far ase , , 7
- C, 8 22 wy 14
. C 21 ot Las Lea it
~ Cc Bg 289 THE Tn 8
N 2 3 1
co gS 2) Vs t
C, Bi 115 Lie i a
k C 102 S27 Liss i 2
SD N 3 7 4
the in valerie. Intuition after fail Cc. 7 Th So eas
tape | Gers of isomers reaulting from Cc, bo fea B35 iz at
Te pla wrof atoms by the saric nur “ 2 1s Li 3
v ‘ yal 4 “_ C a2 2 bel a 32
ana f vclence, Sorce renre- Sen Vk ay 20
a don Yd NO ? 2
UNO, 28 S495 40
. CON,O, a L 732 O44
rt, the ratio hets ome en ‘ 5 s 3 ,
subs tonen wa. Oe tintt- CN LO as TA a 1?
sutwtitation, eg NO: CN.O, > : aad 76
- NO, 10 23
CN,O, S600 G05 137
NO, 240-72 1
N.O, 3 3
= CN O 17 a4
CESCUIS SION ea ef oe an
S CLNO, 1G DAG 1iG
NCH, S 15
The variations of ivasers with C.3.,0 TO Ly
Nurebers 4 afore. : tor ton count or with ~ 24
til offre ater Evpe er can be rationalized or C a 34
the zh tL ke 4 ethos fig gee othe N 1 ~
et ! , JR eh, eb oe N 5