Hi,

I went through the list of values you quoted and I am surprised y= ou are talking of big differences. Sincerely, you theoretical values are we= ll comparable to the experimental values. What happend was a simple 180 deg= ree rotation in the plane of molecule, perhaps this happened while modeling= your molecule. Hence, the negative values. You can just take the magnitude= s. The last value that seemed largely different is actually 89 degree (if y= ou subtract it from 180 degree by which the molecular plane was rotated).

Best re= gards.

Olasunkanmi Lukman Olawale

Current Add= ress:
Depa= rtment of Chemistry,
Obafemi Awolowo= University,
Ile-Ife, Osun State.
Nigeria.

+234-0-80-52401564 Or +234-0-80-67161091

On Tuesday, 12 November 2013, 12:15, N. Sukumar nagams__rpi.ed= u <owner-chemistry(0)ccl.net> wrote:

Sent to CCL by: "N. Sukumar" [nagams_-_rpi.edu]
By = adding 2pi (360deg) to it (as Hugo has already explained).

N. Sukuma= r
Professor of Chemistry
Shiv Nadar University, India
----------------------------
"Pursue something so important th= at even if you fail, the world is better
off with you having tried." --= Tim O'Reilly
http://as.wiley.com/WileyCDA/WileyTit= le/productCd-0470769009.html
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3DOriginal message text=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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 you= r comment on my question in CCL.
in some of torsional angles we have dif= ferences in a negative sign. How
can I ignore this sign.

Rega= rds,
shojaei

> "Hugo Alejandro Jimenez Vazquez hji= menez[*]woodward.encb.ipn.mx" wrote:
>
> Sent to CCL by:= Hugo Alejandro Jimenez Vazquez
[hjimenez^_^woodward.encb.ipn.mx]
> This message i= s in MIME format. The first part should be readable text,
>&nbs= p; while the remaining parts are likely unreadable without MIME-aware tool= s.
>
> ---862666845-1686960974-1384055120=3D:5311
> Cont= ent-Type: TEXT/PLAIN; CHARSET=3DISO-8859-1; format=3Dflowed
> Content= -Transfer-Encoding: QUOTED-PRINTABLE
> Content-ID: <Pine.LNX.4.64.= 1311092147191.5385(a)woodward.encb.ipn.mx>
>
>
> To = be sincere, I do not see those "big differences" you mention. If you=3D20> take into account that the negative angles can be converted to posit= ive by=3D
> =3D20
> adding 360, what you have is:
>
&= gt; 175.1 vs. 184.0
> 178.9 vs. 183.0
> 17= 7.0 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=3D
> =3D20
> r= easonable amount; out of all the others, the first one differs the most,=3D=
> =3D20
> by less than 10=3DB0.
>
> I have no ide= a about what your molecule looks like. In addition, you do=3D20
> not= mention how you got the experimental values, but I would assume they=3D20<= br>> came from an X-ray diffraction structure. You should be aware that = the=3D20
> gas phase structure (from the calculations) does not neces= sarily have to=3D20
> be exactly the same as the structure in the cry= stal. In the solid phase=3D20
> the geometry is influenced by nonbond= ed interactions with all the=3D20
> neighbouring molecues which might= lead to a slight or severe changes with=3D
> =3D20
> respect t= o the gas phase structure, particularly in floppy molecules.
>
&g= t; The gas phase geometry obtained through calculation also depends on the= =3D20
> level of theory employed, something that you do not mention either.
>
>= ; Regards,
>
> ---
> Hugo A. Jimenez Vazquez
> hji= menez(a)woodward.encb.ipn.mx
> Departamento de Quimica Organica
&g= t; ENCB-IPN
> Mexico
>
>
> On Sat, 9 Nov 2013, Ha= mid 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=3D
> etical
> > and exper= imental torsion angles.
> >
> > Torsion angle=3D09 = Experimental=3D09Theoretical
> > N(2)C(2)C(3)C(8)= =3D09 175.1=3D09 -175.965
> > O(1)C(2)C= (3)C(4)=3D09 178.94=3D09 -177.005
> > C= (8)C(3)C(4)N(3)=3D09177.0 179.837
>= > C(2)C(3)C(4)C(5)=3D09 178.73=3D09 -177.808
&= gt; > C(31)N(3)C(4)C(3)=3D09 174.2=3D09 169.= 686
> > C(4)N(3)C(31)C(32)=3D09 91.0=3D09 = ; 138.193
> >
> >
> > Any idea explainin= g such a differences is highly appreciated.
> >
> >
&g= t; >
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