GAS –PHASE SYNTHESIS COLUMN CHROMATOGRAPHY AND VISIBLE SPECTROSCOPY OF 5, 1, 15, 20 - TETRAPHENYLPORPHYRIN.

Experiment 7 : GAS -PHASE SYNTHESIS COLUMN CHROMATOGRAPHY AND VISIBLE SPECTROSCOPY OF 5 , 1 , 15 , 20 - TETRAPHENYLPORPHYRIN

SUFFOLK UNIVERSITY , 2007

DORIS I .VESCHI

Thank you

GAS -PHASE SYNTHESIS COLUMN CHROMATOGRAPHY AND VISIBLE SPECTROSCOPY OF 5 , 1 , 15 , 20 - TETRAPHENYLPORPHYRIN

Introduction

In this experiment , porphyrin is synthesized through non-solvent reaction conditions using benzaldehyde and pyrrole as starting materials

Porphyrins are molecules that play essential roles in the biological systems . Iron-containing porphyrins called hemes are important in the oxygen-carrying activity of hemoglobin . Other systems in which porphyrin plays an

important role include the electron transport chain reactions and photosynthesis reactions

Preparation of porphyrin is started by building its carbon framework- porphyrinogen . Porphyrinogen is built by a substitution reactions between pyrrole and benzaldehyde . After the framework has been established , porphyrinogen is then oxidized to yield the desired product-porphyrin . Porphyrin is a fully conjugated aromatic compound with18 electrons

Figure 1 : Synthesis of mesotetraphenylporphyrin via high temperature reaction conditions

Figure 2 : Porphyrin assembly from eight electrophilic aromatic substitution reactions

Determination on the purity of the obtained compound was done through both spectral and chromatographical analyses . Chromatographic techniques done for the purification of porphyrin include Thin Layer Chromatography (TLC ) and Column Chromatography . Spectral analysis was done through the use of UV-Visible Spectroscopy . This experiment aims to synthesize 5 , 1 15 , 20 -Tetraphenylporphyrin via solvent-less gas phase reaction and analysis through TLC , column chromatography and visible spectral analysis

Procedure

This experiment was carried out by capping a 5 ml conical vial with a septum bearing screw cap . The vial was then placed in a heating mantle filled with sand , where 1 .5 inches of the vial was submerged in the sand . Heat was then applied to the sand bath , and when the temperature of the bath reached 170 ?C , a 2 micro liter syringe was used to inject 10 micro liter of benzaldehyde through the septum . When the temperature reached to 180 ?C , a 10 micro liter syringe was used to inject 7 micro liters of pyrrole through the septum . Then the temperature of the sand was raised to 250 ?C . The vial was heated at 250 ?C for 15 min , and was left to cool down at room temperature afterwards . After the vial was cooled down a 1- ml of CH2Cl2 was used to rinse the cap liner and walls of the vial

Figure 3 : Schematic diagram of gas phase reaction synthesis of TPP

Thin layer Chromatography (TLC

Thin-layer chromatography (TLC ) was used as a technique for identifying compounds , determining their purity and following the progress of a reaction . It also permits the optimization of the solvent system for a given separation problem . As stationary phase , a special finely ground matrix silica gel was coated on a glass plate , a metal or a plastic film as a thin layer 0 .25 mm . In addition , a binder like gypsum was mixed into the stationary phase to make it stick better to the slide . A 7 1 mixture of hexane / ethyl acetate was prepared . A small amount of solvent...