JCE Online Journal of Chemical EducationDivision of Chemical Education, American Chemical SocietyAmerican Chemical Society
 | Subscriptions  | Software Orders  | Support  | Contributors  | Advertisers  | 

JCE Print
   Current Issue
 Previous Issues
 Supplements
 Search JCE Index

JCE Digital Library
   ChemInfo
 DigiDemos
 Featured Molecules
 LivTexts
 LrnCom
 QBank
 SymMath
 WebWare

JCE Software
   Latest Releases
 Software & Video
 Downloads
 Support

Only@JCE Online
   JCE Online Store
 JCE HS CLIC
 JCE Discussion Forums
   Biographical Snapshots
 ChemEd Resource Shelf
 Featured Molecules
 Hal's Picks
 Project Chemlab
 Reviewed WWW Sites
 "Web-Ed" Articles

About JCE
   Features
 Publications
 Operations
 Outreach
 Contact Us


  Home > JCE Print > Journal of Chemical Education > Issues > 1996  > March  >
Features
Tested Demonstrations
The Effect of Solvent and Micelles on the Rate of Excited-State Deprotonation
Charles J. Mazzacco
Department of Physical Science, Rhode Island College, Providence, RI 02908
Cover
March 1996
Vol. 73 No. 3
p. 254
Abstract
This article describes a demonstration of the effect of solvent and micelles on the rate of excited-state deprotonation of the 8-hydroxyprene-1,3,6-trisulfonate (HPTS) ion. As is typical of hydroxy-aromatic molecules and ions, this ion is a weak acid in its ground electronic state but becomes a much stronger acid in its lowest excited singlet state. The ground and excited state pKas of the HPTS ion are 7.4 and 0.4, respectively. Thus, at pHs in the range between 3 and 6, the acid form of the HPTS ion tends to deprotonate when it becomes electronically excited. However, the rate of this excited-state deprotonation is very solvent dependent. In aqueous solution, the rate of excited-state deprotonation of the acid form of the ion is much faster than fluorescence and nonradiative decay. Thus, the ion emits almost exclusively from its conjugate base form which exhibits a green emission with a lamda max at 510 nm. In solvents with high ethanol content, the rate of excited-state deprotonation is much slower than that in aqueous solution and emission occurs mainly from the acid form of the ion. In such solvents, HPTS exhibits a violet emission with a lambda max at 455 nm which is characteristic of the acid form of the ion. The demonstration described in this article illustrates the colorful changes that occur in the fluorescence of HPTS when the solvent is changed from a mostly alcohol to a mostly aqueous solution. It also illustrates the effect that cetyltrimethylammonium bromide (CTAB) micelles have on the fluorescence of this ion.
More Information
*  Citation
 Mazzacco, Charles J. J. Chem. Educ. 1996 73 254.
*  Keywords
*  History
 Created:
Last Updated:		 9/23/1999
2/22/2006
<< Previous Article Table of Contents Next Article >>
  Home > JCE Print > Journal of Chemical Education > Issues > 1996  > March  > Page 254


Subscriptions
 Subscription Info
 Order Forms

JCE HS CLIC

Our Secondary School editors work hard to distill all the JCE materials to produce a fraction of particular interest to high school teachers. We call it CLIC.
 JCE HS CLIC

Contributions Welcome
JCE welcomes your submission
 Contributors' Corner

Advertisers
In recent years we have worked hard to better match our advertisers with our readers. When shopping for chemistry education materials, visit our advertisers' WWW sites first.
 Recent Advertisers

Be An Ambassador
Take JCE along on your outreach missions. Copies of the Journal, guest access to JCE Online, our publications catalog, and more are available for your participants.
 Outreach with JCE

Comments to
jceonline@chem.wisc.edu		 Copyright © Division of Chemical Education, Inc., American Chemical Society.
All rights reserved.