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Effect of Acid on Hydrolysis

Printed From: Sol-Gel Gateway
Category: Sol-Gel Forum
Forum Name: Chemistry
Forum Discription: General Discussion on Sol-Gel Chemistry, Precursors Reactivity, Chemical Reactions Paths (Hydrolysis, Polycondensation, Chemical Additives effects, etc)
URL: http://www.solgel.com/sgforum/forum_posts.asp?TID=1087
Printed Date: 21 May 2013 at 2:06pm

Topic: Effect of Acid on Hydrolysis

Posted By: Solcalibur
Subject: Effect of Acid on Hydrolysis
Date Posted: 16 January 2007 at 4:11am

Hello

I have a question

I'm studying about preparing Sol-gel Solution by mix TTIP(Titanium(4) Isopropoxide) with Ethanol(Solvent) but i want to decrease rate of hydrolysis, so i mix this solution with Acetic acid . I don't know why acid have an effect on hydrolysis reaction.

Can anyone explain me about this(Effect of acid on Hydrolysis of TTIP) ? Thank you very much.

Replies:

Posted By: Nano
Date Posted: 16 January 2007 at 1:38pm

The purpose to add acid is to slow down the condensation reaction, not the hydrolysis.
Actually, hydrolysis is accelerated with acid.

Posted By: Solcalibur
Date Posted: 17 January 2007 at 2:39am

I think i must have a misunderstood for a long time, i thought that the acid should reduce the hydrolysis reaction.

Anyway, do you have any reference or source ? Because i explain this to my advisor. He didn't believe me. He told me to get the ref. I don't know how to find the ref. about relation of acid with the hydrolysis or gelation. Can anyone help me ? Thanks

Posted By: Nano
Date Posted: 17 January 2007 at 10:56am

Here is a link for the hydrolysis of silane at differnt pH values. The sol-gel reaction of TTIP is expected to be simliar to silane except the former is much faster. For TEOS/TMOS, the hydrolysis completes within seconds in highly acid solution, while it may take hours in netrual solution.
http://www.psrc.usm.edu/mauritz/solgel.html - http://www.psrc.usm.edu/mauritz/solgel.html .
Or you can check Brinker's Sol-Gel Science book for detail.
btw, to slow donw the hydrolysis of TTIP, you can add a chelating reagent such as ACAC (check the previous posts) to make the TTIP bulky.

Posted By: majidkazemi
Date Posted: 20 January 2007 at 9:14am

please send me answer of question

best regard

Posted By: majidkazemi
Date Posted: 20 January 2007 at 9:44am

I used TiCl4 as precursor for the preparation of titania thin films by sol gel method in my MSc Research work.. I m not an expert but i used some tips to handle TiCl4 which you can try.

while pouring TiCl4 in any solvent (alcohol) keep ur solvent in an ice bath so the vapors of TiCl4 can condence and react properly.I did not use any special mechanisim while handling it. Just perform the reaction in fuming hud and use any glass delivery tube for transfering it. Dont forget to use mask and gloves cz its vapours are very irritating to skin and dangerous to lungs.

And always store TiCl4 in refrigerator so that its vapours can condense.

As for as dilution is concerned, i dont know much about it because i used concentrated but i think it cannt be diluted with water because of its vigorous reaction with water.

If you are reacting it with any alcohol, perform the reaction in any inert solvent which may be benzene.

hope these tips can help you in handling it.

Chaji's tips are also effective.

Posted By: Parth
Date Posted: 21 February 2007 at 10:30pm

Can anyone plz explain role of ethanol in titania synthesis from TTIP?

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With regards,
Parth

Posted By: Nano
Date Posted: 22 February 2007 at 10:14am

Ethanol acts mainly as a solvent. There may be some alcoholysis reactions between TTIP and ethanol T-OR + EthOH----T-OEth + ROH. But it is not important in most cases.

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