CHM 2210 Organic Chemistry Green Extraction of Natural Products Presentation Hello, this project(presentation) is for organic chem lab. I have uploaded all

CHM 2210 Organic Chemistry Green Extraction of Natural Products Presentation Hello, this project(presentation) is for organic chem lab. I have uploaded all the instructions bellow please go through them carefully . And I will be uploading the handout an two files in order to complete this assignment successfully. Any question needed please let me know because this assignment worth a lot of grading points .

Important

Choose one of these two articles to evaluate for your presentation:

You can choose on of these two papers , choose whatever you’re comfortable to

Paper 1.pdf

Paper 2.pdf

Start with the handout, and here are more specific instructions:

Create a PowerPoint that summarizes one of the two papers and answers the questions from the instructions handout
10 slides minimum, including Title slide and References slide (you can use as many slides as you like, but if there are more than 20, you’re probably overdoing it)
Title slide should include paper name with authors, and your name as the author of the presentation
Reference slide at the end should include a full reference for the main paper (not the large block of references used in the paper itself — those are the paper’s references, not yours).
If you include a figure or any information from the paper that has a citation, you should cite it like the main paper did and include that reference in your References slide. If you use any outside reference (another paper, a website, etc.) as supporting data, you should include that in the Reference slide as well.
No more than 1 of the 10 slides should be filled with a large figure (the table or graph you evaluate). You may include as many other figures and images as you like, just add extra slides if they take up space (in other words, you can’t fill up the 10 slide minimum with figures)
Avoid “filler” slides — for example, do not use a whole slide just for the title of a section
“Creativity and delivery” from the instruction handout means to make slides aesthetically pleasing and organized: Don’t stuff them so full of text that I can’t read them, use a design (not plain white slides), vary the slide layout, adjust font sizes to make sense, proofread, balance the slides (use the space…don’t squish everything into the middle and leave the slide mostly empty, but also don’t cram every slide full), make sure I can see the figures. Basically, you can earn points just for making it look interesting and nice. Think about how the PowerPoint should look if you were actually presenting it.
The sections under “Reviewing the Article” could make good titles for slides.
It’s a PowerPoint, so bullet-points and brief, meaningful statements are the idea.
There are 5 questions under “Reviewing the Article” – DON’T FORGET TO ANSWER THEM. It’s fine to list these questions and answer them directly.
“Reviewing the Article” directs you to answer the 5 questions “in detail.” This doesn’t mean to use a bunch of words; it means to use chemistry detail or supporting information, not just a “yes” or “no” answer. Write meaningful statements, but not huge sentences or paragraphs.
No more than 1 direct quotation from the paper is permitted. Quotations are not required, but if you choose to include one, keep it brief (rewriting concepts in your own words is what demonstrates understanding of material).
Grading: overall presentation appearance, organization, following instructions, clarity, demonstrating understanding of the paper, effective summary, answering the questions thoughtfully, appropriate chemistry detail, and proper references will count. You’ve spent the semester learning to analyze and discuss, so say something meaningful, follow the requirements, organize it well, and you’ll do fine.
Presentations will be uploaded in PowerPoint format and scanned by TurnItIn, so do not cut and paste text – use your own words. Do not convert to pdf. Journal of Liquid Chromatography & Related Technologiesw, 28: 2499–2513, 2005
Copyright # Taylor & Francis, Inc.
ISSN 1082-6076 print/1520-572X online
DOI: 10.1080/10826070500189638
Chiral Separations of Ibuprofen and
Propranolol by TLC. A Study of the
Mechanism and Thermodynamics
of Retention
M. Sajewicz, R. Pie˛tka, and T. Kowalska
Institute of Chemistry, Silesian University, Katowice, Poland
Abstract: In contrast with gas and column liquid chromatography, both of which
enable very efficient separation of enantiomers, thin-layer chromatography (TLC)
has never proved particularly successful in the same field. This can be regarded as
puzzling because although the performance of TLC is substantially lower than that
of the instrumental modes of chromatography, it still seems efficient enough to
ensure even difficult separations of pairs of analytes. There is a steady demand for
simple, inexpensive, and successful chiral separations, preferably executed with the
aid of TLC. The best proof of this is a few documented and promising attempts
reported by reliable laboratories in developing countries. Some of these reports,
however, describe experiments performed with glass plates coated in the laboratory,
which gives rise to questions regarding the accuracy and repeatability of the results
obtained. Similar concerns are evoked by traditional visualization of the outcome of
a separation by use of dyeing agents, rather than by densitometry (which furnishes concentration profiles of the bands and the possibility of in-situ identification also). In this
study, we have repeated chiral separations of two widely used drugs, ibuprofen and propranolol, adapting working conditions reported elsewhere to a system based on standardized and commercially available chromatographic plates. We also performed
detection and identification on the developed chromatograms by means of densitometry. In our experiments with the modified chromatographic procedures, the results
obtained proved at least as good as those reported in the original papers and occasionally somewhat better. For both ibuprofen and propranolol, preliminary thermodynamic
evaluation of the standard chemical potentials of adsorption (Dma) for each of the two
enantiomers considered was also performed. The results obtained look promising and
Address correspondence to T. Kowalska, Institute of Chemistry, Silesian University, 9 Szkolna Street, Katowice, Poland. E-mail: kowalska@us.edu.pl
2499
2500
M. Sajewicz, R. Pie˛tka, and T. Kowalska
realistic; it seems that adsorption TLC can be used in the future for thermodynamic
assessment of the racemization process.
Keywords: TLC, Silica gel sorbent, L -Arginine impregnation, Enantiomer separations,
S-(þ)- and R-(2)-ibuprofen, S-(2)- and R-(þ)-propranolol
INTRODUCTION
Chiral separations are among the most demanding and challenging experimental tasks in the separation sciences, and for this particular purpose gas chromatography (GC) and column liquid chromatography (LC) are both employed.
Planar chromatography, however, is used much less frequently than its column
liquid counterpart because of its relatively poorer separation performance
compared to the column mode. Thin layer chromatography (TLC) is, on the
other hand, an invaluable tool in multiple pharmaceutical analyses and in
pharmaceutical quality control, and chirality is commonplace among drugs.
Even these superficial considerations readily lead to the simple yet sound conclusion that more effort—both theoretical and practical—ought to be invested
in adapting planar chromatography for successful handling of enantiomer
separations.
The objective of the work described in this paper was to modify procedures described elsewhere,[1,2] that enabled the chiral separation of the
enantiomers of ibuprofen and propranolol on laboratory-prepared TLC
plates to contemporary practice of using commercial precoated glass plates
and densitometric detection. The mechanisms of retention and energetics of
the two separations are discussed.
EXPERIMENTAL
Chiral Separation of Ibuprofen
Test Analytes
Our experiment was performed with two different test analytes: R, S-(+)ibuprofen and S-(þ)-ibuprofen (Sigma – Aldrich, St Louis, MO, USA; cat.
#I-4883 and #I-106, respectively). Solutions of R, S-(+)-ibuprofen and of
the S-(þ) enantiomer were prepared at a concentration of 1 mg mL21 (ca.
5.8 1023 mol L21) in 70% ethanol, and 10-mL volumes were applied to
the plates, side-by-side. The R, S-(+)-ibuprofen sample contained two
antipodes, which we intended to separate effectively. The sample of S-(þ)ibuprofen was meant as an external standard, marking the position of one
antipode. Because R-(2)-ibuprofen is no longer commercially available
there was virtually no chance of using a second external standard. The
Chiral Separations of Ibuprofen and Propranolol by TLC
2501
chemical structures of the two ibuprofen enantiomers separated in this experiment are presented in Figure 1.
Commercial TLC Silica Gel Layers and Their Pretreatment
We used commercial glass TLC plates precoated with 0.25 mm layers of silica
gel 60 F254 (Merck, Darmstadt, Germany; cat. #1.05715). Before use, the
plates were washed by predevelopment with methanol –water, 9 : 1 (v/v)
and then dried at ambient temperature for 3 h. Washing of the plates before
initiating more sensitive separations is often recommended by the
manufacturer.
The washed and dried plates were then impregnated with a
3 1022 mol L21 solution of L -arginine in methanol by conventional
dipping. This procedure was different from that used in the original
paper,[1] which consisted of direct addition of L -arginine to the silica gel
slurry before coating of the glass plates. The concentration of the impregnating solution was calculated to deposit on the adsorbent layer the same
amount of amino acid as previously reported.[1]
One-Dimensional Development
The impregnated chromatographic plates with adjacent spots from 10 mL
volumes of the solutions of R, S-(+)-ibuprofen and the S-(þ) enantiomer
were developed to a distance of 15 cm using the ternary mobile phase
recommended in the original paper [1], i.e., acetonitrile (ACN) – methanol
Figure 1. General structure of ibuprofen and demonstration of its chirality.
2502
M. Sajewicz, R. Pie˛tka, and T. Kowalska
(MeOH) –H2O (5 : 1 : 1) plus several drops of acetic acid to adjust the pH to 4.8.
After development, the plates were dried in an ambient atmosphere for 3 h and
the two lanes—one for R, S-(+)-ibuprofen and the other for the S-(þ) counterpart—were scanned densitometrically. The results obtained (as RF values) are
given in Table 1. This experiment was repeated at least five times.
Two-Dimensional Development
Plates with a single 10 mL spot of the R, S-(+)-ibuprofen solution at the corner
were developed to a distance of 15 cm in the first direction with ACN –
MeOH – H2O (5 : 1 : 1) plus several drops of acetic acid as the mobile phase.
The plates were then dried in an ambient atmosphere for 3 h, and 10 mL of
the solution of the S-(þ) enantiomer was applied to the origin of the second
direction of development, adjacent to the first, already developed, sample.
The chromatograms were developed to a distance of 15 cm in the second
direction (perpendicular to the first) with the same mobile phase. After development, the plates were again dried in an ambient atmosphere, and the
developed lanes were scanned densitometrically. This experiment was
repeated at least five times.
Densitometric Assessment of Separation Performance for S-(þ)- and
R-(2)-Ibuprofen
The separation of the two ibuprofen enantiomers (as measured by the
numerical values of the retardation factor, RF) was evaluated by densitometry.
Densitograms were acquired with a Desaga (Heidelberg, Germany) model CD
60 densitometer equipped with Windows-compatible ProQuant software.
Concentration profiles of the developed lanes were recorded in ultraviolet
(UV) light from the deuterium lamp (in the reflectance mode) at 210 nm.
This wavelength corresponded fairly well with the more pronounced
maximum of the two in the UV spectrum of ibuprofen. The dimensions of
the rectangular light beam were 0.02 mm 0.4 mm. The maxima of the
Table 1. Numerical values of Dma estimated for S-(þ)- and R-(2)-ibuprofen chromatographed on silica gel with ACN– MeOH – H2O (5 : 1 : 1) adjusted to pH 4.8 by
addition of a trace amount of acetic acid as the mobile phase
Enantiomer
RF
Dma
[kJ mol21]
DDma
[kJ mol21]
First
S-(þ)
R-(2)
0.82
0.79
21.9
22.3
0.4
Second
S-(þ)
R-(2)
0.83
0.76
21.7
22.8
1.1
Development direction
Chiral Separations of Ibuprofen and Propranolol by TLC
2503
separated concentration profiles of the two species were used for calculation of
RF values.
As well as recording the densitograms and calculating RF and DRF values
to produce evidence of improved enantioseparation, the densitometer was also
used to record UV absorption spectra of the separated chromatographic bands
directly from the plates (i.e., in situ). It was intended to use these spectra as
direct proof of satisfactory separation, because one expects identical UV
absorption spectra from any two enantiomers making a pair of antipodes.
Chiral Separation of Propranolol
Test Analyte
This part of our experiment was performed with R, S-(+)-propranolol (Astra
Hässle, Molndal, Sweden; cat. #1393) as the test analyte. A solution of R, S(+)-propranolol was prepared at a concentration of 1 mg mL21 (ca.
3.3 1023 mol L21) in 70% ethanol, and 10 mL volumes were applied to
the plates (this was our normal solution). Because the amount of the S-(2)
enantiomer in this mixture was very low (ca 5%), we also prepared a three
times more concentrated (i.e., fortified) solution of the same sample
(1 1022 mol L21; applied to the plate as 10 mL volumes). The fortified
solution contained a substantial concentration overload of R-(þ)-propranolol
(resulting in a characteristic triangular peak shape), but the larger amount of
the S-(2) antipode facilitated monitoring of the separation process. The
chemical structures of the two propranolol enantiomers separated in this
experiment are presented in Figure 2.
Commercial TLC Silica Gel Layers and Their Pretreatment
For separation of the two enantiomers of propranolol, the same commercially
available TLC silica gel layers as described above for ibuprofen were used.
Their further modification (i.e., predevelopment with the methanol – water
mixture and then impregnation with a solution of 3 1022 mol L21
L -arginine in methanol) was also different from that described in the
original paper,[2] although the same as described above for ibuprofen.
One-Dimensional Development
Chromatographic plates with spots from 1 mL volumes of the normal and
fortified solutions of R, S-(+)-propranolol were developed to a distance of
15 cm with the binary mobile phase recommended in the original paper,[2]
i.e., ACN-MeOH (15 : 4) containing strictly controlled and relatively small
amounts of aqueous ammonia (NH3 . H2O), namely 0, 50, 100, 300, 400,
500, and 1000 mL. Apart from investigating the chiral separation itself, the
impact of the amount of an added ammonia on the overall enantiomer
2504
M. Sajewicz, R. Pie˛tka, and T. Kowalska
Figure 2.
General structure of propranolol and demonstration of its chirality.
separation procedure was also investigated. The results obtained (as RF values)
and their dependence on the amount of ammonia added and on mobile phase
pH are given in Table 2. This experiment was repeated at least five times.
Two-Dimensional Development
Plates with a single 10 mL spot of R, S-(+)-propranolol solution at the corner
were developed to a distance of 15 cm in the first direction, with ACN – MeOH
Table 2. Numerical values of Dma estimated for S-(2)- and R-(þ)-propranolol chromatographed in the first direction on silica gel with ACN – MeOH (15 : 4) containing
trace amounts of aqueous ammonia as the mobile phase
Mobile phase
Volume of
NH3 . H2O (mL)
0
50
100
300
400
500
1000
RF (+0.02)
Dma (kJ mol21)
pH
S-(2)
R-(þ)
S-(2)
R-(þ)
DDma
(kJ mol21)
7.75
10.2
10.7
10.8
10.9
10.9
11.0
0.01
0.02
0.02
0.03
0.04
0.03
0.02
0.11
0.12
0.12
0.14
0.16
0.16
0.18
216.9
215.2
215.2
214.2
213.4
214.2
215.2
210.8
210.5
210.5
210.1
29.7
29.7
29.4
6.1
4.7
4.7
4.1
3.7
4.5
5.8
Chiral Separations of Ibuprofen and Propranolol by TLC
2505
(15 : 4) plus 400 mL aqueous ammonia as the mobile phase. The plates were
dried in an ambient atmosphere for 3 h and the chromatograms were again
developed to a distance of 15 cm in the second direction (perpendicular to
the first) with the same mobile phase. After development, the plates were
dried for the second time in an ambient atmosphere, and the developed
lanes were scanned densitometrically. This experiment was repeated at least
five times.
Densitometric Assessment of Separation Performance for S-(2)- and
R-(þ)-Propranolol
The procedure was analogous to that described above for ibuprofen. Concentration profiles of the developed chromatograms were recorded at 210 nm,
which corresponded fairly well with the wavelength of the more pronounced
maximum in the UV spectrum of propranolol.
RESULTS AND DISCUSSION
Chiral Separation of Ibuprofen
Densitometric Profiles of the Developed Lanes
A typical densitogram obtained from one-dimensional development is given
in Figure 3. On this densitogram, the positions of S-(þ)-ibuprofen and its
R-(2) antipode are clearly marked.
After numerous replicate one-dimensional developments, we evaluated
the mean retardation factors (RF) of the two enantiomers and, from the
areas under the respective concentration profiles, the relative proportions of
the enantiomers. The mean RF values were 0.82 (+0.02) for S-(þ)ibuprofen and 0.79 (+ 0.02) for its R-(2) counterpart. This result is in
agreement with data reported elsewhere[1] (the RF values for twicedeveloped S-(þ)- and R-(2)-ibuprofen were reported to be 0.80 and 0.77,
respectively). Quantitative analysis (i.e., estimation from relative areas)
showed our (+) mixture to contain approximately 10% R-(2)-ibuprofen, in
agreement with literature reports of the enantiomeric composition of the commercial form of this drug (i.e. of R, S-(+)-ibuprofen).
Densitometry, after development in the second direction, enabled further
assessment of the resolution of the two ibuprofen antipodes. The respective
mean RF values were 0.83 (+0.02) for S-(þ)-ibuprofen and 0.76 (+0.02)
for its R-(2) counterpart. After the two-dimensional development, resolution
of the two antipodes was enhanced to DRF ¼ 0.07.
To obtain better insight into the substantially enhanced chiral separation
of S-(þ)-ibuprofen from its R-(2) counterpart (compared with that obtained
by Bhushan and Parshad[1]) and into the “skewed” arrangement of the two
2506
M. Sajewicz, R. Pie˛tka, and T. Kowalska
Figure 3. Typical densitogram obtained from one-dimensional development, with
the positions of the S-(þ) and R-(2) antipodes of ibuprofen marked.
species on the chromatographic plate, the three-dimensional (3D) presentation
of part of the TLC plate with the two development directions indicated (as 1
and 2) is given in Figure 4. This illustration was obtained by densitometric
scanning (in parallel 1-mm intervals) of the 15-mm wide track in the
second direction of development of the chromatogram.
Densitometric UV In Situ Identification of Separated S-(þ)- and
R-(2)-Ibuprofen
The most persuasive proof of successful separation of the two enantiomers is
in situ identification of the resolved chromatographic bands, e.g., by acquiring
their UV absorption spectra. In such circumstances, one can justifiably expect
two identical spectra. The identical UV absorption spectra of the two chromatographic bands marked in Figure 3 as S-(þ)- and R-(2)-ibuprofen are illustrated in Figure 5 by the single spectrum of R-(2)-ibuprofen (i.e., the antipode
with the lower abundance in the racemic mixture investigated and, hence, considerably more challenging to record).
The UV spectrum shown in Figure 5 is identical with that of S-(þ)ibuprofen (the only difference between the two is the different intensity of
the absorption bands, because of the different amounts of the two separated
species on the adsorbent layer). It was, thus, clearly proven that the two
resolved chromatographic bands are of two enantiomers present in different
quantitative proportions and yet with identical chemical structure (except
for the spatial arrangement of the substituents around the asymmetric
carbon atom). This result provides up-to-date instrumental confirmation of
successful complete TLC separation of the two ibuprofen antipodes.
Chiral Separations of Ibuprofen and Propranolol by TLC
2507
Figure 4. 3D representation of part of the TLC plate with the two directions of development, 1 and 2, indicated. Densitometric scanning as described in the text was performed to illustrate better the separation performance and the “skewed” arrangement
of S-(þ)-ibuprofen relative to its R-(2) counterpart.
Figure 5. The in situ UV spectrum of the chromatographic band of R-(2)-ibuprofen
measured from the chromatogram densitometrically recorded and shown in Figure 3.
2508
M. Sajewicz, R. Pie˛tka, and T. Kowalska
On the Mechanism and Thermodynamics of the Chiral Separation
of Ibuprofen
Trace amounts of acetic acid were added to the ternary mobile phase to
maintain its pH at the solid-liquid interface at 4.8, i.e., well below the pI (isoelectric) point of L -arginine (10.8), thereby maintaining the impregnating
amino acid in the cationic form. Because ibuprofen is a carboxylic acid
(Figure 1) and, therefore, apt to dissociate (and form an organic anion), the
mechanism of chiral discrimination in the system discussed can generally
be viewed in terms of the energy difference for ion-pair formation (i.e., in
the formation of the two diastereomeric salts) according to the scheme:
þ S-ðþÞ-ibuprofenðanionÞ $ion pair
ðthermodynamically characterized by K1 Þ
L-arginine
L-arginine
ðcationÞ
ðcationÞ
ð1Þ
þ R-ðÞ-ibuprofenðanionÞ $ion pair
ðthermodynamically characterized by K2 Þ
ð2Þ
Separation of the two enantiomers of ibuprofen can be achieved only
because the thermodynamic equilibrium constants (K) for the ion-pairformation process for the two enantiomers (K1 and K2, respectively) have
different numerical values (K1 = K2).
From the theory of adsorption liquid chromatography it is well known[3]
that the thermodynamic equilibrium constant of adsorption, K, can be defined
as:
log K ¼ Dma =ð2:303RTÞ
ð1Þ
where Dma is the standard chemical potential for adsorption of the analyte on
the adsorbent surface, R is the universal gas constant, and T is the temperature
of the experiment. From the chromatographic results (i.e., RF values) obtained
for the two ibuprofen enantiomers and keeping in mind another fundamental
relationship of adsorption liquid chromatography,[3] namely:
RF ¼ 1=ð1 þ K fÞ
ð2Þ
where f is the so-called phase ratio (i.e., the ratio of the volume of the
adsorbed mobile phase to the volume of the flowing mobile phase), we
estimated the thermodynamic magnitudes of Dma for S-(þ)- and R-(2)ibuprofen; these are given in Table 1. In our calculation, we assumed f is
approximately equal to 0.1; T was measured as 2958K.
From the numerical values of Dma given in Table 1 it is clearly evident
that the affinity of R-(2)-ibuprofen for the adsorbent layer is considerably
greater than that of its enantiomeric antipode. This readily apparent difference
between the standard chemical potentials of adsorption of the two antipodes is
evidently because of their different ability to form ion pairs, although the energetics of ion-pair formation and the energetics of adsorption of ibuprofen’s
Chiral Separations of Ibuprofen and Propranolol by TLC
2509
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