The studyofthehealingpowerofchemicalcompounds, present into the known
natural active principles and its subsequent use, shall be seen
initially as a pseudoscientificprocedure,
acontinuationoftheChineseandArabianoccultism, whichwasbased
inthepercentagecontentoffire, air, earthandwater, aswellas
ontheassociatedqualities: hot-cold, humid-dry. . .,
whichthematterwassupposed to be formed by. Themethod, possessingroots in
Hippocrates, Dioscoridesand Galen was studied, described and polished by
Avicenna, Averrot!s, Bacon and Villanova inthe MiddleAge.
Italsowasappearingasastudyconstantduringthe renaissance and after. On
the other hand, the birthofchemistry asascientific offspring from
alchemy propitiated alternative ways ofknowledge in order to solve the
same problem. In this manner, in the past century, approximately hundred
years from now, Sylvester proposed the first molecular description in
numerical discrete form, employing ideas which even in present times can
be associated withinthesocalledmoleculartopology.
Sylvester'stopologicalmodel can be considered the seed allowing the
originofthis big tree, which is now knownastheoreticalchemistry. .
During all the past time from the first topological modelofSylvester up
to now, the proliferationofnumerical parameters to describe molecular
structures has not ceased to grow larger. Some ofthese parameters have
played a very important role for the understandingofthe organic
molecules behavior and, by extension, for the comprehension and
evaluation of their physical as well as biologicalproperties.
InthemindofeveryspecialistaretheHammett'scr, theTaft constantsor the
octanol-water partition coefficient. Other numerical parameters,
suchasthosederivedfromthemodemtopologicalmolecularrepresentationarein
aprocessofconstantrevisionandgrowing. Thus, theHosoyaandRandicindices,
ortheKier'sconnectivities, amongseveralnotsowellknownnumericaldataare
usual reference descriptors. They are putatthe researchers' disposition,
andare easily deducible from any molecular representation in form
ofordered setsof numerical figures. All ofthem are profusely studied and
employed in present times. The main idea consists into the useofthese
numerical data in orderto
obtaininformationonthemoleculartrendstopossessoracquirecertainproperties
and, even better than this, to determine in which degree or intensity
molecules presenteverything.
