Paul+DeGregory+-+log


 * Assignment 1: 5 properties each from 5 independent sources of molecule of my choice**


 * N,N-diethylethanamine (Triethylamine)**

__Melting Point__ -115 °C [|WolframAlpha] [|IPCS InChem] [|Alfa Aesar] -114.7 °C [|Wikipedia] [|CRC Handbook of Chemistry and Physics]

__Boiling Point__ 88.8 °C [|WolframAlpha] 89.7 °C [|Wikipedia] 89 °C [|CRC Handbook of Chemistry and Physics] [|IPCS InChem] 89-90 °C [|Alfa Aesar]

__Density__ 0.726 g/(cm)^3 [|WolframAlpha] [|Wikipedia] 0.7275 g/(cm)^3 (at 20 °C) [|CRC Handbook of Chemistry and Physics] 0.726 g/(cm)^3 (at 20 °C) [|Alfa Aesar] Raw Data Value: 0.726 g/mL (at 25 °C) Converted Value: 0.726 g/(cm)^3 (at 25 °C) [|Sigma-Aldrich]

__Vapor Pressure__ Raw Data Value: 51.74 mmHg (at STP) Converted Value: 6.898 kPa (at STP) [|WolframAlpha] 7.2 kPa (at 20 °C) [|IPCS InChem] [|NIOSH]**[convert to common unit also JCB]** Raw Data Value: 51.75 mmHg (at 20 °C) Converted Value: 6.899 kPa (at 20 °C) [|Sigma-Aldrich] Raw Data Value: 57.07 mmHg (at 25 °C) Converted Value: 7.609 kPa (at 25 °C) [|Scorecard]

__Flash Point__ -6.667 °C [|WolframAlpha] -15 °C (closed cup method) [|Wikipedia] -7 °C [|CRC Handbook of Chemistry and Physics] -17 °C [|IPCS InChem] -11 °C [|Alfa Aesar]


 * Assignment 2: Summary of article for project.**
 * Article: [|DOI to Article] **
 * [Full Marks JCB]**

__"Summary" Paragraph__ - Derivatives of cyclodextrins with hydroxypropyl, methyl, or carboxymethyl groups result in increased aqueous solubility of the cyclodextrins and increased stabilization of cyclodextrin-analyte complexes via hydrogen bonding. - At pH values below 4, carboxymethylated cyclodextrin can be used in separations similarly to uncharged cyclodextrins while at pH values above 5, the derivatized cyclodextrin can be used to separate uncharged enantiomers.

__Page 1 Paragraph 1__ - During the 1980s and early 1990s developments in capillary electrophoresis allowed it to become an efficient separation technique. - Many different separation modes of capillary electrophoresis have been used and the use of capillary electrophoresis to separate chiral compounds is of interest.

__Page 1 Paragraph 2__ - Promising methods for separating enantiomers in capillary electrophoresis include the use of micelles to form chiral detergents, bile salt systems, and cyclodextrins. - Derivatization of cyclodextrins can greatly affect recognition and resolution of enantiomers.

__Page 1 Paragraph 3__ - For the experiments performed, a P/ace System 2050 from Beckman Instruments, fused silica capillaries from Polymicro Technologies, hydroxypropylated cyclodextrins from Wacker Chemie, other cyclodextrins from Cyclolab, enantiomeric samples from the pharmaceutical department of the university at which the experiments were performed, deionized water from a Milli-Q system, and analytical grade chemicals from different supplies were used. - The fused silica capillaries were coated with 4% T linear polyacrylamide, which resulted in coatings on the inner capillary wall that suppressed significant electroosmotic flow (EOF) for several months as long as buffers up to pH 7 were used.

__Page 2 Paragraph 1__ - The increase in separation power of enantiomers by cyclodextrin derivatives compared to that of cyclodextrins that have not been derivatized can be explained by the increase in the difference of the binding constants between each enantiomer and the cyclodextrin for cyclodextrin derivatives. - The OH groups on the rim of the cyclodextrin cavity control the orientations of enantiomers in analyte-cyclodextrin complexes and thus derivatization of these groups causes changes in the binding constants between the cyclodextrins and analytes.

__Page 2 Paragraph 2__ - Hydroxypropyl and carboxymethyl groups increase the aqueous solubility of cyclodextrins allowing for the utilization of a broad range of concentrations in optimizing separations, although cyclodextrin concentrations above 20% (w/v) result in very viscous solutions that increase separation time and may decrease resolution. - The separation of a racemic mixture of dansylated D,L-phenylalanine was performed on a coated fused silica capillary and was dependent on cyclodextrin concentration, as the mixture was separated using 0.3% (w/v) hydroxypropylated β-cyclodextrin (HPBCD) while slightly lower and slightly higher concentrations of the cyclodextrin did not produce separations. - Spiking the racemic mixture with dansylated L-phenylalanine showed that the migration order of the two enantiomers reversed as HPBCD concentration increased from 0.5% (w/v) to 15% (w/v). - Repeating the separation of the racemic mixture of dansylated D,L-phenylalanine on an uncoated capillary showed that separation could be achieved at a high electrophoretic mobility of the two enantiomers, that resolution and electrophoretic mobility decreased as HPBCD concentration was increased beyond the range in which separation occurred, and that the migration order of the two enantiomers reversed as HPBCD concentration was further increased.

__Page 2 Paragraph 3__ - At low concentrations of HPBCD the migration order of the D and L enantiomers of dansylated D,L-phenylalanine can be explained by the difference in the binding constants of the enantiomers with HPBCD. - At high concentrations of HPBCD the migration order of the D and L enantiomers of dansylated D,L-phenylalanine can be explained by the lack of dissociation of the analyte-HPBCD complexes of both enantiomers and the different charge densities of the enantiomer-HPBCD complexes.

__Page 3 Paragraph 1__ - Coated capillaries that reduce the EOF allow for analyte-cyclodextrin complexes to have longer migration times, allowing for more time for the reversible complexation of the analytes with the cyclodextrin and thus increasing resolution while permitting the use of shorter capillaries. - The differing resolution, migration time, and peak shape of three separations of the enantiomers of hexobarbital using three different cyclodextrins demonstrated that analytes with higher affinities to cyclodextrins require more time to elute. - Differences in the resolutions of the separations of the enantiomers of hexobarbital were due to differences in the binding constants of the enantiomers with different cyclodextrin derivatives, which affect the steric fitting of enantiomers in the cyclodextrins.

__Page 3 Paragraph 2__ - Triangular peaks in capillary electrophoresis are typically due to disparities between the mobilities of the background electrolyte and the analyte and can be corrected by using a buffer with a mobility that better matches that of the analyte. - Three different buffer systems were examined, of which the mobility of a citric acid buffer displayed the best match to that of the analytes, allowing for better peak shapes and thus higher efficiencies and better resolution. - Altering the concentration of the cyclodextrin in the buffer can eliminate disparities between background electrolyte and analyte mobilities but may significantly reduce the separation of enantiomers.

__Page 3 Paragraph 3__ - Hydroxypropylated γ-cyclodextrin was the best chiral selector for the enantiomers of a dihydropyridine derivative, exhibiting high enantiomeric selectivity, which could be explained by hydrogen bonding between the analyte and cyclodextrin and favored steric fitting of the analyte into the cyclodextrin. - The high resolution obtained for the separation of the enantiomers of the dihydropyridine derivative enables capillary electrophoresis to be used to control the substance’s purity.

__Page 4 Paragraph 1__ - At pH values below 4, carboxymethylated β-cyclodextrin (CMBCD) acts as an uncharged cyclodextrin as all of its carboxylic groups, which provide hydrogen bonding capability and strong steric discrimination between analytes, are protonated. - The separation of the enantiomers of three drugs used in cough medicines took place in under 10 minutes using CMBCD and resulted in a different migration order and better resolution of the analytes than when HPBCD was used due to the greater polarity of the carboxymethyl groups in CMBCD compared to the hydroxypropyl groups in HPBCD.

__Page 4 Paragraph 2__ - CMBCD was used to separate the enantiomers of ephedrine in cough syrup, which demonstrates that the separation of compounds within a complex, viscous matrix is possible, although difficult, as the low conductivity of viscous samples causes voltage drop, Joule heating, bubble formation, and current drop at the sample plug.

__Page 5 Paragraph 1__ - At a pH above 5, CMBCD is anionic and has an electrophoretic mobility, which prohibits the separation of anions and allows for the separation of cations due to ion-pairing.

__Page 5 Paragraph 2__ - At pH values above 5, CMBCD is capable of separating neutral enantiomers. - Without CMBCD the enantiomers of oxazolidinone derivatives moved with the EOF in an uncoated capillary while with 1% (w/v) CMBCD and at a pH of 6 the enantiomers did not move with the EOF and were able to be resolved.

__Page 5 Paragraph 3__ - Use of a coated capillary, reversal of polarity, and other optimization steps allowed for better resolution of the enantiomers of oxazolidinone derivatives in shorter times when CMBCD was used as a chiral selector.

__Page 5 Paragraph 4__ - Different derivatizations of cyclodextrins have different chiral selectivities. - Cyclodextrins are able to separate enantiomers due to differences in the binding constants of enantiomers with cyclodextrins and due to differences in mobility between the enantiomer-cyclodextrin complexes.

__Page 5 Paragraph 5__ - Higher efficiencies and resolutions can be achieved by matching the mobilities of the background electrolyte to those of the enantiomers.

__Page 5 Paragraph 6__ - Charged cyclodextrins can separate uncharged analytes. - Further work will be done to examine the potential of charged cyclodextrins to act as ion-pairing agents.

Considering doing my paper on the use of cyclodextrins in chiral separations.
 * [Very interesting topic - you might also look at cyclodextrins as chiral catalysts if you need to expand a bit JCB]**

Paper Topic: Use of cyclodextrins in separations of enantiomers in capillary zonal electrophoresis.

Applications/Importance -of CDs (brief) -of CDs in CE separations (especially CZE)

Structure of CDs -3 natural CDs (alpha, beta, gamma) -CD derivatives -why make derivatives -properties that derivation can give CDs in separations in CE

Two types of enantiomeric separations in CE with CDs -direct (emphasis) -indirect

Theory -inclusion complexation -effects of other interactions -hydrogen bonding with -OH groups on structure while outside of cavity -van der Waals forces -binding constants -mobility of analyte -mobility of analyte-complex

Changing separation parameters -pH -temperature -buffer concentration -optimal concentration of cyclodextrin (for direct..) -cyclodextrin concentration -3 different binding models (low, medium, high affinity) -what causes difference in mobility to level off at high CD conc.

Effects of changing cyclodextrin -effects of 3 identical groups in 2,3,6 positions etc... -any "best" cyclodextrins? do some have a broader application range? -why?

Strategies for selecting appropriate cyclodextrin for the separation -e.g. highly sulfated cyclodextrins very versitle and dimethyl, trimethyl derivatives are complementary....

Conclusions

-potentially useful further studies?
 * [I just came across this application of [|cyclodextrins as "Velcro"] - it isn't catalysis but still you might find it interesting JCB]**


 * Images for final paper:**