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Y2KK update: This ISU does not belong to me. It belongs
to my sister, VivF. This was her Grade 13 Chemistry ISU project
and I'm posting it on the internet so that I'll never lose it.
I hope the little one is having so much fun at Western University...
Click Here for the Microsoft
Word '97 Doc
On research:
Though this ISU may not have resulted
in final, finished products, nonetheless, valuable knowledge
was gained. It is the compilation of research that is the main
body of this ISU, in which lies an almost complete body of references
for this ISU topic. Two References which I thought were extremely
useful are:
1. The Chemistry of Flavonoids Compounds
(Geissman) - which completely outlined the fundamental components
that is important to know about flavonoids. Descriptions on
each flavonoid family is given as well as charts on solvents
that are useful, which bring out flavonoid colour and chromatographic
analysis on flavonoids.
2) Biology of Canadian Weeds: Linaria Vulgaris. (Saner)
- Due to the fact that there is very little knowledge on Linaria
Vulgaris, this is an extremely important article in that it outlines
most of the physical characteristics and behaviour of this plant.
Other important references were the
books containing articles from various flavonoid symposium which
gives some indication to the experiments being performed on flavonoids
as well as the references on chromatography and crystallization
which provide methods for these processes.
On Experimental Data:
Much of the information that I gathered
experimentally involved the physical and chemical characteristics
of the sample as well as many useful hints on how to handle this
sample in the future. One of the major problems during the crystallization
process was the fact that the methanol in the solution evaporated
much too quickly for a good crystal sample to form. In the future
a mixture of water-methanol or some other solvent must be used
to slow down the evaporation rate. Water has a much higher vapour
point and may help to alleviate the problem. As a result, the
sample was constantly oxidized and became useless. Flavonoids
are known to be free-radical scavengers and easily bond with
oxygen.
Upon analyzing the flavonoid with other solvents, it was found
that the sample placed in ethanol was soluble (completely white
and splashes of yellow along the borders of the container), while
when placed in with butanol was less soluble (the result was
an opposite effect). Ethanol and butanol are both carbon based
compounds.
Fig. 14 Structure of Butanol Fig.
15 Structure of Ethanol
The solubility of the samples into
these compounds is due to the polarity of both the solvents and
the sample. The dipole moment of ethanol is much stronger than
that of butanol because the length of the carbon chain neutralizes
the effect of the negative ~OH group. The fact that the sample
was more soluble in ethanol indicates that it has a very strong
polarity, following the chemist's rule that "like dissolves
like" (Van Hook, p. 193). The ethanol-water mixture resulted
in the separation of the solution into 2 components. Since the
outside ring was white and the inside ring yellow, it is assumed
that the outer component is more polar than the inner one. Finally,
the butanol-water mixture resulted in the most successful results
as it separated the sample into 3 components, white outer layer,
yellow intermediate layer, and an orange center. The orange
component is a resulting azeotrope of the first two. Azeotropes
are residues formed from the combination of 2 mixtures. Azeotropes
have their own boiling points and a composition midway between
its parent compounds. The fact that there are 2-3 components
in the sample makes sense since the flowers of linaria contain
both linarin and pectolinarin as well as other constituents.
Future experiments should consider the use of butanol as a solvent.
During the crystallization process, white precipitates began
to form along the bottom of the container. This could have
been the result of contamination or the natural occurrence during
the crystallization process resulting in a purer sample. This
is a common occurrence when trying to crystallize a compound
by evaporation since the solution may become "saturated
with respect to other solutes and separate as gum, oil, or amorphous
solid and contaminate the crystals"(Van Hook, p.396). When
this happens recrystallization is necessary.
As mentioned previously in the introduction, certain characteristics
of molecules are favoured for crystallization. These are the
presence of high, permanent dipole moments, spherically shaped
molecules, and possessing a low molecular weight. Linarin is
a very polar molecule, however, it is also very long-shaped and
extensive in structure which may account for some of the difficulty
in crystallization.
As for the extraction of flavonoids from the stems and leaves
of linaria, it was found that a 3% w/v solution of sodium chloride-water
was successful in dissolving glucoside flavonoids. The resulting
mixture was a yellow-green colour (fig.13) which indicates that
it also contains many of the flavonoids present in the flowers:
linarin and pectolinarin. Thus, these flavonoids are distributed
throughout the plant. The glucosides must also be polar due
to the ionic (Na+, Cl-) and polarity (H2O) of the solution.
However, it was unfortunate that I was unable to advance past
this point. Unlike methanol, the sodium-chloride solution did
not prevent the solution from bacterial degradation. Note that
for future experiments that the solution cannot sit for more
than a day.
In conclusion, though I was not able to see any finalized results,
many interesting aspects about the sample were discovered, as
well as information about other flavonoids which exist throughout
the plant. Those that wish to continue this ISU should consider
looking at the glucosides of linaria vulgaris carefully, as it
is the known to be insectically active and consequently will
have many applications.
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