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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: tiffae on August 05, 2017, 10:20:25 PM

Title: Enthalpy of combustion
Post by: tiffae on August 05, 2017, 10:20:25 PM

Hi all,

I'm a year 11 IB student in Australia and I'm currently doing an IA on enthalpy of combustion of alcohols. I've chosen to do 1-propanol, 2-propanol and 2-methyl-2-propanol.

I thought tertiary alcohols would have the highest enthalpy of combustion followed by secondary than primary.(because of the surface area) But apparently that's not the case? In the IB data booklet, 2-propanol's enthalpy of combustion is -2010 but -2020 for 1-propanol. Can anyone explain to me why is it the case???? I really appreciate it, thanks!!!

Title: Re: Enthalpy of combustion
Post by: XeLa. on August 10, 2017, 05:49:50 PM

What do you know about the difference in bonding between 1-propanol, and 2-propanol? Do you think that would affect the enthalpy of combustion?

XeLa

Title: Re: Enthalpy of combustion
Post by: Vidya on August 11, 2017, 12:31:19 AM

Compare bond strength of C-OH on the basis of  formation of free radical/carbocation  after homolytic /heterolytic bond cleavage.More stable is the radical or Carbocation more easy to break  bond or weak is  bond.I think this will help you in comparing Heats of Combustions of primary, Secondary and tertiary alcohols.