Green chemistry reactions in Duhok City : part I rose bengal solar photosensitized synthesis of juglone

Abstract EN

Green chemistry is to carry out chemical activity e.g.

chemical reaction and disposal, such that hazardous substances will not be used and generated.

To study the effect of geographical location and solar light intensity difference on the reaction time between Cologne- Germany, Dublin -Ireland and Duhok- Iraq, we have reinvestigated the photoreaction of oxygenation of 1, 5-dihydroxy naphthalene to give juglone (5- hydroxyl-1, 4-naphthoquenone) using Rose Bengal as a sensitizer.

The reaction time to accomplish the end of reaction was (2.5 hours) with 77.5 % yield, while the time and yield of the same reaction in Cologne and Dublin being (4 hours and 79 %) and (3 hours and 69 %) respectively.

The mechanism of photooxygenation is via the reaction of Rose Bengal in the triplet excited state with ground state oxygen which is normally in triplet state to produce excited singlet state oxygen that photo oxygenates 1, 5-dihydroxy naphthalene to produce juglone.

The reaction proceeds via a [4 + 2]-cycloaddition followed by a break-down of the endo- peroxide intermediate.

The reaction was followed up by TLC and UV -Visible spectroscopy.

The product was characterized by infra-red and UV -Visible spectroscopy.