From owner-chemistry@ccl.net Tue Nov 12 05:53:00 2013 From: "N. Sukumar nagams__rpi.edu" To: CCL Subject: CCL: Differences between theoretical and experimental torsion angles Message-Id: <-49331-131112054919-11543-l0o1/zYzWwGvVfzY6L4t+Q=server.ccl.net> X-Original-From: "N. Sukumar" Content-Disposition: inline Content-Transfer-Encoding: binary Content-Type: text/plain Date: Tue, 12 Nov 2013 5:49:40 -0500 MIME-Version: 1.0 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 ---------------------------- "Pursue something so important that even if you fail, the world is better off with you having tried." -- Tim O'Reilly http://as.wiley.com/WileyCDA/WileyTitle/productCd-0470769009.html ==============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. > > ---862666845-1686960974-1384055120=:5311 > Content-Type: TEXT/PLAIN; CHARSET=ISO-8859-1; format=flowed > Content-Transfer-Encoding: QUOTED-PRINTABLE > Content-ID: > > > 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. > > > > > > > ---862666845-1686960974-1384055120=:5311--http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt===========End of original message text===========