Cyclodextrins!

A powerpoint presentation- 4-05-05:evening

Presenting-Addison CarterAdvisor- Dr David Kammler

Cyclodextrins:

α-cyclodextrin- 5 sugar moleculesβ-cyclo-dextrin- 6 sugar moleculesγ-cyclodextrin- 7 sugar molecules

Simply cyclized α-d-1,4-glucopyranose sugar

Utility to HumansCentered in the Torus shaped form, differing interior sizes allow for encapsulation of many target compounds.

β-cyclo-dextrin

Nonpolar centralcavity

Secondary Hydroxyl rim

Primary Hydroxyl Rim

An ether-like central section creates ideal conditions forpreferential spacial arrangement of non-polar compoundsin the central section

The exterior wall retains polar (hydrophilic) sugar-likecharacter which allows for solubility of the cyclodextrin molecule both with and without a guest molecule

Bacillus CirculansCyclodextrin glucosyltransferase- Extracted v. in situ

In reaction vats at pH 6.0-7.0 at 35-40 °C.

The source of cyclodextrins

Within starch producing plants

Targets:

Real World AppsDrugs

-solubility-photostability-oxidation prevention-ease of handling

Synthesis-site-selective binding-chiral selectivity-general protecting group

Real World Apps II Environmental Problems

-well water contamination-hypothetically use for heavy metal contamination

Chemical Analysis with HPLC-selective complexation with different target substrates allows for different flow rates for the various target substrates

Enzyme Mimicry?

Polymerization

Terephthalic acid polymerization

Methyl MethacrylatePolymerization

Phase Typed Polymerization

Bulk Solution

Emulsion Dispersion

One Phase

Two Phase

Trouble with polymerization

Surfactants-used in emulsion polymerization, one of the main modes of plastic production-phosphate/sulphate anion base

The problem: Not many readily available natural break down paths

Alternative Mode to Emulsion PolymerizationDispersion Polymerization:

Non-polar Polar

Some small number of monomericunits move into the aqueous phaseto be polymerized.

-rate-polydispersity-phase separation

Essentially this is the question of how much monomer will transverse the interstitial zone between the oiland water layers

A Potential Solution: Cyclodextrins as Phase

Transfer Agents

Non-Polar

Polar

Complexation

Polymerization

InitiatorIn this the cyclodextrin modulates the transverse activity of the monomer.

So then, what's the next Question, Considering:-dispersion polymerization is well documented

-with many substrates-in many solvent pairs-with some phase transfer catalysts

-only one person will be working on this project as a four credit class over the course of a semester

-numbers on the equilibria of substrates/substrate-cyclodextrin pairs is not readily available

-we do not have an NMR available to examine complexation

however,

-we do have a Ultraviolet-Visible spectrophotometric machine -cyclodextrin doesn't absorb UV-Vis spectrum light

Thus,

-We can find concentrations of photo responsive chemicals in solution

-in the aqueous layer (as well as the organic layer)with and without Cyclodextrin for each of our targetmolecules

-partition coefficients for those solvated chemicals

AbsorptionMolar AbsorptionConstant

Length of Absorbing sample

Concentrationof absorbing sample

Substrate Choice

- UV-active- polymerizable- soluble- complexable- available from the local stock of chemicals

All these are either mono- or di- substitutedbenzene rings which are known to be quiteUV-active. They are also cheap and polymerizable

Styrene Terephthalic acid p-aminobenzoic acid

p-pentylstyrene

Para-amino benzoic acid(PABA)

-Locally available-PABA is very UV active-soluble in water-soluble in ethyl acetate

The problem

-Too UV active in Ether, Ethyl Acetate, Water, 1-Octanol.1 M?.01 M?.001 M?.0001 M?

Dilution to this level allowed for a scale within machine detection limits.- Not an effective use of time considering the interest was to study partitioning with an eye toward polymerization which would be served via other routes

Terephthalic Acid, the First alternateProblem:Solubility

.1 M

.01 M

.001 M

Styrene, the Second Alternative

Unfortunately past this molarity the accuracy of the scale would be called into question for the amount of solvent that was acceptable.

Problem: Time-Only preliminary testing at .01 M was conducted however absorbance was within the detection envelope for the instrument.-Much lower prep time would result in larger volume of data

AKA: The 1.5 month time warp

AnInterlude

Concerning the Repair of a Certain Piece of Instrumentation

Vital!to the Continuation of Senior Project

Epsilon Values of PABA in Four SolventsDetermined at .0001M PABA in named solvent

E In Ether

EEE In Ethyl Acetate

In Water

In 1-octanol

20180 at 275 nm

11970 at 284 nm

15650 at 275 nm

13480 at 266 nm

Values taken at the most convenient location along the graph of absorptivity, λ max.

Partitioning Behavior Compared With and without cyclodextrin

.264 at 273nm

.268 at 273nm1 M equivalent CD

Amount of Cyclodextrin the issue?

.202 at 276nm

10 Molar equivalents of cyclodextrin presentyields lower absorbancethan the previous 1 Molar equivalent system

-instead of complexing with the PABA the peak shifting right may be a sign of ethyl acetate complexation

The Road from here:Choice in substrate

-late found resources have recipes in which pure substrate is used as the non-polar phase

example:styrene ON aqueous cyclodextrin mixed -mono-substituted benzene rings-biphenyl

Time to mix-late found materials point to time scale of days for complexation

Substituted cyclodextrin-better match