CCL: Differences between theoretical and experimental torsion angles

 Sent to CCL by: "N. Sukumar" [nagams_-_rpi.edu]
 By adding 2pi (360deg) to it (as Hugo has already explained).
 N. Sukumar
 Professor of Chemistry
 Shiv Nadar University, India
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 ==============Original message text===============
 On Sun, 10 Nov 2013 5:08:07 EST "Hamid Shojaei shojaei81^gmail.com"
 wrote:
 Sent to CCL by: "Hamid  Shojaei" [shojaei81**gmail.com]
 Dear Dr. Hugo Alejandro Jimnez Vzquez,
 Thank you very much for your comment on my question in CCL.
 in some of torsional angles we have differences in a negative sign. How
 can I ignore this sign.
 Regards,
    shojaei
 > "Hugo Alejandro Jimenez Vazquez hjimenez[*]woodward.encb.ipn.mx"
 wrote:
 >
 > Sent to CCL by: Hugo Alejandro Jimenez Vazquez
 [hjimenez^_^woodward.encb.ipn.mx]
 >   This message is in MIME format.  The first part should be readable text,
 >   while the remaining parts are likely unreadable without MIME-aware tools.
 >
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 >
 >
 > To be sincere, I do not see those "big differences" you mention.
 If you=20
 > take into account that the negative angles can be converted to positive by=
 > =20
 > adding 360, what you have is:
 >
 >   175.1 vs. 184.0
 >   178.9 vs. 183.0
 >   177.0 vs. 179.8
 >   178.7 vs. 182.2
 >   174.2 vs. 169.7
 >    91.0 vs. 138.2
 >
 > At least for me, only the values for the last angle differ by a more than=
 > =20
 > reasonable amount; out of all the others, the first one differs the most,=
 > =20
 > by less than 10=B0.
 >
 > I have no idea about what your molecule looks like. In addition, you do=20
 > not mention how you got the experimental values, but I would assume they=20
 > came from an X-ray diffraction structure. You should be aware that the=20
 > gas phase structure (from the calculations) does not necessarily have to=20
 > be exactly the same as the structure in the crystal. In the solid phase=20
 > the geometry is influenced by nonbonded interactions with all the=20
 > neighbouring molecues which might lead to a slight or severe changes with=
 > =20
 > respect to the gas phase structure, particularly in floppy molecules.
 >
 > The gas phase geometry obtained through calculation also depends on the=20
 > level of theory employed, something that you do not mention either.
 >
 > Regards,
 >
 > ---
 > Hugo A. Jimenez Vazquez
 > hjimenez(a)woodward.encb.ipn.mx
 > Departamento de Quimica Organica
 > ENCB-IPN
 > Mexico
 >
 >
 > On Sat, 9 Nov 2013, Hamid Shojaei Shojaei81..gmail.com wrote:
 >
 > >
 > > Sent to CCL by: "Hamid  Shojaei" [Shojaei81-#-gmail.com]
 > > Dear All,
 > >
 > > I do some structural calculations but I see big differences between
 theor=
 > etical
 > > and experimental torsion angles.
 > >
 > > Torsion angle=09       Experimental=09Theoretical
 > > N(2)C(2)C(3)C(8)=09 175.1=09        -175.965
 > > O(1)C(2)C(3)C(4)=09 178.94=09        -177.005
 > > C(8)C(3)C(4)N(3)=09177.0          179.837
 > > C(2)C(3)C(4)C(5)=09 178.73=09        -177.808
 > > C(31)N(3)C(4)C(3)=09 174.2=09         169.686
 > > C(4)N(3)C(31)C(32)=09  91.0=09         138.193
 > >
 > >
 > > Any idea explaining such a differences is highly appreciated.
 > >
 > >
 > >
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