From owner-chemistry@ccl.net Fri Apr 5 06:19:00 2013 From: "Jean Jules Fifen julesfifen _ gmail.com" To: CCL Subject: CCL:G: how to calculate energy in kcal/mol for a particular temperature Message-Id: <-48531-130405060014-27834-nc2KB1/NdWwT/6tkkI9Pew]_[server.ccl.net> X-Original-From: Jean Jules Fifen Content-Type: multipart/alternative; boundary=e89a8f23440f4c7de704d99a266b Date: Fri, 5 Apr 2013 10:59:57 +0100 MIME-Version: 1.0 Sent to CCL by: Jean Jules Fifen [julesfifen===gmail.com] --e89a8f23440f4c7de704d99a266b Content-Type: text/plain; charset=ISO-8859-1 You can do all the above calculations at a given temperature. Just add the appropriate keyword in your input file. For gaussian: #... temperature=343.15 With best regards, On 5 April 2013 06:13, John Keller jwkeller|alaska.edu < owner-chemistry{:}ccl.net> wrote: > Hi Ashutosh, > You can use the Eyring-Polanyi equation to calculate k the unimolecular > rate constant, given Gibbs Free Energy of Activation delGdoubledagger. > Google "Eyring equation wiki" to see the equation written out. > > To a good approximation at moderate temperatures, the free energy of > activation is not dependent on temperature. Reactions go faster at higher > temperatures because a higher proportion of molecules have attained a > kinetic energy greater or equal to the free energy of activation. > > To estimate free energy of activation, you would need to optimize and do > frequency calculation for the starting compound and transition state, and > take the difference in free energies between these two. Locating the T.S. > is sometimes difficult: if you are using Gaussian, the Opt=TS, or OPT=QST2, > or Opt=QST3 methods are used. > > Good luck! > John Keller > > > > On Thu, Apr 4, 2013 at 7:17 PM, ashutosh gupta ashu1809 a gmail.com < > owner-chemistry]~[ccl.net> wrote: > >> Dear All, >> >> Normally it is assumed that if the activation barrier is less than 20 >> kcal/mol, then the reaction occurs at ROOM TEMPERATURE. >> >> how do we calculate it? >> what is its formula? >> >> how can we know corresponding energy in kcal/mol for some other >> temperature say 70 degree Celsius. >> >> thanking you. >> >> kind regards and best wishes >> ashutosh >> varanasi India >> > > -- *J. Jules Fifen.* Deo On 5 April 2013 06:13, John Keller jwkeller|alaska.edu < owner-chemistry{:}ccl.net> wrote: > Hi Ashutosh, > You can use the Eyring-Polanyi equation to calculate k the unimolecular > rate constant, given Gibbs Free Energy of Activation delGdoubledagger. > Google "Eyring equation wiki" to see the equation written out. > > To a good approximation at moderate temperatures, the free energy of > activation is not dependent on temperature. Reactions go faster at higher > temperatures because a higher proportion of molecules have attained a > kinetic energy greater or equal to the free energy of activation. > > To estimate free energy of activation, you would need to optimize and do > frequency calculation for the starting compound and transition state, and > take the difference in free energies between these two. Locating the T.S. > is sometimes difficult: if you are using Gaussian, the Opt=TS, or OPT=QST2, > or Opt=QST3 methods are used. > > Good luck! > John Keller > > > > On Thu, Apr 4, 2013 at 7:17 PM, ashutosh gupta ashu1809 a gmail.com < > owner-chemistry]~[ccl.net> wrote: > >> Dear All, >> >> Normally it is assumed that if the activation barrier is less than 20 >> kcal/mol, then the reaction occurs at ROOM TEMPERATURE. >> >> how do we calculate it? >> what is its formula? >> >> how can we know corresponding energy in kcal/mol for some other >> temperature say 70 degree Celsius. >> >> thanking you. >> >> kind regards and best wishes >> ashutosh >> varanasi India >> > > -- *J. Jules Fifen.* On 5 April 2013 06:13, John Keller jwkeller|alaska.edu < owner-chemistry{:}ccl.net> wrote: > Hi Ashutosh, > You can use the Eyring-Polanyi equation to calculate k the unimolecular > rate constant, given Gibbs Free Energy of Activation delGdoubledagger. > Google "Eyring equation wiki" to see the equation written out. > > To a good approximation at moderate temperatures, the free energy of > activation is not dependent on temperature. Reactions go faster at higher > temperatures because a higher proportion of molecules have attained a > kinetic energy greater or equal to the free energy of activation. > > To estimate free energy of activation, you would need to optimize and do > frequency calculation for the starting compound and transition state, and > take the difference in free energies between these two. Locating the T.S. > is sometimes difficult: if you are using Gaussian, the Opt=TS, or OPT=QST2, > or Opt=QST3 methods are used. > > Good luck! > John Keller > > > > On Thu, Apr 4, 2013 at 7:17 PM, ashutosh gupta ashu1809 a gmail.com < > owner-chemistry]~[ccl.net> wrote: > >> Dear All, >> >> Normally it is assumed that if the activation barrier is less than 20 >> kcal/mol, then the reaction occurs at ROOM TEMPERATURE. >> >> how do we calculate it? >> what is its formula? >> >> how can we know corresponding energy in kcal/mol for some other >> temperature say 70 degree Celsius. >> >> thanking you. >> >> kind regards and best wishes >> ashutosh >> varanasi India >> > > -- *J. Jules Fifen.* On 5 April 2013 06:13, John Keller jwkeller|alaska.edu < owner-chemistry{:}ccl.net> wrote: > Hi Ashutosh, > You can use the Eyring-Polanyi equation to calculate k the unimolecular > rate constant, given Gibbs Free Energy of Activation delGdoubledagger. > Google "Eyring equation wiki" to see the equation written out. > > To a good approximation at moderate temperatures, the free energy of > activation is not dependent on temperature. Reactions go faster at higher > temperatures because a higher proportion of molecules have attained a > kinetic energy greater or equal to the free energy of activation. > > To estimate free energy of activation, you would need to optimize and do > frequency calculation for the starting compound and transition state, and > take the difference in free energies between these two. Locating the T.S. > is sometimes difficult: if you are using Gaussian, the Opt=TS, or OPT=QST2, > or Opt=QST3 methods are used. > > Good luck! > John Keller > > > > On Thu, Apr 4, 2013 at 7:17 PM, ashutosh gupta ashu1809 a gmail.com < > owner-chemistry]~[ccl.net> wrote: > >> Dear All, >> >> Normally it is assumed that if the activation barrier is less than 20 >> kcal/mol, then the reaction occurs at ROOM TEMPERATURE. >> >> how do we calculate it? >> what is its formula? >> >> how can we know corresponding energy in kcal/mol for some other >> temperature say 70 degree Celsius. >> >> thanking you. >> >> kind regards and best wishes >> ashutosh >> varanasi India >> > > -- *J. Jules Fifen.* --e89a8f23440f4c7de704d99a266b Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
You can do all the above calculations at a g= iven temperature. Just add the appropriate keyword in your input file. For = gaussian: #... temperature=3D343.15

With best regards,


On 5 April 2013 06:13, John Keller j= wkeller|alaska.edu <= owner-chemistr= y{:}ccl.net> wrote:
Hi Ashutosh,
You can use the Eyring-Polanyi = equation to calculate k the unimolecular rate constant, given Gibbs Free En= ergy of Activation delGdoubledagger. Google "Eyring equation wiki"= ; to see the equation written out.

To a good approximation at moderate temperatures, the free energy= of activation is not dependent on temperature. Reactions go faster at high= er temperatures because a higher proportion of molecules have attained a ki= netic energy greater or equal to the free energy of activation.

To estimate free energy of activation, you would need to optimize= and do frequency calculation for the starting compound and transition stat= e, and take the difference in free energies between these two. Locating the= T.S. is sometimes difficult: if you are using Gaussian, the Opt=3DTS, or O= PT=3DQST2, or Opt=3DQST3 methods are used.

Good luck!
John Keller



On Thu, Apr 4, 2013 at 7:17= PM, ashutosh gupta ashu1809 a gmail.com <owner-chemistry]~[ccl.net> wrote= :
Dear All,

Normally it is assumed that if the activation barrier i= s less than 20 kcal/mol, then the reaction occurs at ROOM TEMPERATURE.

how do we calculate it?
what is its formula?=

how =A0can =A0we know corresponding energy in kcal/mol = for some other temperature say 70 degree Celsius.=A0

thanking you.

kind regards and best wishes=A0
ashutosh
varanasi India




--
J. Jules Fifen.
Deo



On 5 Ap= ril 2013 06:13, John Keller jwkeller|alaska.e= du <owner-chemistry{:}ccl.net> wrote:
Hi Ashutosh,
You can use the Eyring-Polanyi = equation to calculate k the unimolecular rate constant, given Gibbs Free En= ergy of Activation delGdoubledagger. Google "Eyring equation wiki"= ; to see the equation written out.

To a good approximation at moderate temperatures, the free energy= of activation is not dependent on temperature. Reactions go faster at high= er temperatures because a higher proportion of molecules have attained a ki= netic energy greater or equal to the free energy of activation.

To estimate free energy of activation, you would need to optimize= and do frequency calculation for the starting compound and transition stat= e, and take the difference in free energies between these two. Locating the= T.S. is sometimes difficult: if you are using Gaussian, the Opt=3DTS, or O= PT=3DQST2, or Opt=3DQST3 methods are used.

Good luck!
John Keller



On Thu, Apr 4, 2013 at 7:17= PM, ashutosh gupta ashu1809 a gmail.com <owner-chemistry]~[ccl.net> wrote= :
Dear All,

Normally it is assumed that if the activation barrier i= s less than 20 kcal/mol, then the reaction occurs at ROOM TEMPERATURE.

how do we calculate it?
what is its formula?=

how =A0can =A0we know corresponding energy in kcal/mol = for some other temperature say 70 degree Celsius.=A0

thanking you.

kind regards and best wishes=A0
ashutosh
varanasi India




--
J. Jules Fifen.


On 5 Ap= ril 2013 06:13, John Keller jwkeller|alaska.e= du <owner-chemistry{:}ccl.net> wrote:
Hi Ashutosh,
You can use the Eyring-Polanyi = equation to calculate k the unimolecular rate constant, given Gibbs Free En= ergy of Activation delGdoubledagger. Google "Eyring equation wiki"= ; to see the equation written out.

To a good approximation at moderate temperatures, the free energy= of activation is not dependent on temperature. Reactions go faster at high= er temperatures because a higher proportion of molecules have attained a ki= netic energy greater or equal to the free energy of activation.

To estimate free energy of activation, you would need to optimize= and do frequency calculation for the starting compound and transition stat= e, and take the difference in free energies between these two. Locating the= T.S. is sometimes difficult: if you are using Gaussian, the Opt=3DTS, or O= PT=3DQST2, or Opt=3DQST3 methods are used.

Good luck!
John Keller



On Thu, Apr 4, 2013 at 7:17= PM, ashutosh gupta ashu1809 a gmail.com <owner-chemistry]~[ccl.net> wrote= :
Dear All,

Normally it is assumed that if the activation barrier i= s less than 20 kcal/mol, then the reaction occurs at ROOM TEMPERATURE.

how do we calculate it?
what is its formula?=

how =A0can =A0we know corresponding energy in kcal/mol = for some other temperature say 70 degree Celsius.=A0

thanking you.

kind regards and best wishes=A0
ashutosh
varanasi India




--
J. Jules Fifen.


O= n 5 April 2013 06:13, John Keller jwkeller|al= aska.edu <owner-chemistry{:}ccl.net> wrote:
Hi Ashutosh,
You can use the Eyring-Polanyi equation to calcula= te k the unimolecular rate constant, given Gibbs Free Energy of Activation = delGdoubledagger. Google "Eyring equation wiki" to see the equati= on written out.

To a good approximation at moderate temperatures, the free energy= of activation is not dependent on temperature. Reactions go faster at high= er temperatures because a higher proportion of molecules have attained a ki= netic energy greater or equal to the free energy of activation.

To estimate free energy of activation, you would need to optimize= and do frequency calculation for the starting compound and transition stat= e, and take the difference in free energies between these two. Locating the= T.S. is sometimes difficult: if you are using Gaussian, the Opt=3DTS, or O= PT=3DQST2, or Opt=3DQST3 methods are used.

Good luck!
John Keller



On Thu, Apr 4, 2013 at 7:17= PM, ashutosh gupta ashu1809 a gmail.com <owner-chemistry]~[ccl.net> wrote= :
Dear All,

Normally it is assumed that if the activation barrier i= s less than 20 kcal/mol, then the reaction occurs at ROOM TEMPERATURE.

how do we calculate it?
what is its formula?=

how =A0can =A0we know corresponding energy in kcal/mol = for some other temperature say 70 degree Celsius.=A0

thanking you.

kind regards and best wishes=A0
ashutosh
varanasi India




--
J. Jules Fifen.
--e89a8f23440f4c7de704d99a266b--