From owner-chemistry@ccl.net Thu Sep 20 09:08:00 2018 From: "T. Daniel Crawford crawdad-#-vt.edu" To: CCL Subject: CCL: Strange value for Optical Rotation in g09 Message-Id: <-53468-180919223120-7731-KrRDYl1VhH9mVxORfgCCLg{=}server.ccl.net> X-Original-From: "T. Daniel Crawford" Content-Type: multipart/alternative; boundary="000000000000baec8205764450d6" Date: Wed, 19 Sep 2018 21:30:56 -0500 MIME-Version: 1.0 Sent to CCL by: "T. Daniel Crawford" [crawdad{}vt.edu] --000000000000baec8205764450d6 Content-Type: text/plain; charset="UTF-8" The value of the optical provided by G09 should actually be the specific rotation, i.e. in units of deg/[dm (g/mL)], and thus it is possible to obtain values larger than +/- 360 degrees. There may be a structural reason that one compound gave a large value, e.g. a long-wavelength excitation. -TDC -- Prof. T. Daniel Crawford crawdad ~~ vt.edu On Wed, Sep 19, 2018 at 9:09 PM Eduardo Lemos de Sa edulsa%%ufpr.br < owner-chemistry ~~ ccl.net> wrote: > > Sent to CCL by: "Eduardo Lemos de Sa" [edulsa**ufpr.br] > Dear > > I have performed calculations on g09 aiming to determine optical rotation > values for some organic molecules. Almost results are fine (apparently) > but, one of them pointed me a value of -470.91 (degrees). Of course, I can > add +360 and find a crude value of -110.91 . Please, could you give some > advise if this is correct? > > Thank you in advance > > My best wishes > > Eduardo> > > --000000000000baec8205764450d6 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
The value of the optical provided by G09 should actually b= e the specific rotation, i.e. in units of deg/[dm (g/mL)], and thus it is p= ossible to obtain values larger than +/- 360 degrees.=C2=A0 There may be a = structural reason that one compound gave a large value, e.g. a long-wavelen= gth excitation.

-TDC
--
Prof. T. Daniel Crawford


On Wed, Sep 19, 2018 at= 9:09 PM Eduardo Lemos de Sa edulsa%%ufpr.br= <owner-chemistry ~~ ccl.net= > wrote:

Sent to CCL by: "Eduardo Lemos de=C2=A0 Sa" [edulsa**ufpr.br]
Dear

I have performed calculations on g09 aiming to determine optical rotation <= br> values for some organic molecules. Almost results are fine (apparently) but, one of them pointed me a value of -470.91 (degrees). Of course, I can =
add +360 and find a crude value of -110.91 . Please, could you give some advise if this is correct?

Thank you in advance

My best wishes

Eduardo



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--000000000000baec8205764450d6-- From owner-chemistry@ccl.net Thu Sep 20 09:43:00 2018 From: "Norrby, Per-Ola Per-Ola.Norrby/./astrazeneca.com" To: CCL Subject: CCL: Strange value for Optical Rotation in g09 Message-Id: <-53469-180920005910-21006-QOUuFlCHPhzYDISe1L0CHA{}server.ccl.net> X-Original-From: "Norrby, Per-Ola" Content-Language: sv-SE Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="utf-8" Date: Thu, 20 Sep 2018 04:58:56 +0000 MIME-Version: 1.0 Sent to CCL by: "Norrby, Per-Ola" [Per-Ola.Norrby=astrazeneca.com] No, it’s not correct. For those very strongly rotating, the experiment is performed with dilution, the calculation gives you the standard state value. Helicenes can reach several thousand °, need strong dilution to bring it to a concentration where a traditional polarimeter can measure it. To have a safe experiment, always confirm you have a linear response to dilution. Per-Ola Sent from my iPhone > On 20 Sep 2018, at 04:29, Eduardo Lemos de Sa edulsa%%ufpr.br wrote: > > > Sent to CCL by: "Eduardo Lemos de Sa" [edulsa**ufpr.br] > Dear > > I have performed calculations on g09 aiming to determine optical rotation > values for some organic molecules. Almost results are fine (apparently) > but, one of them pointed me a value of -470.91 (degrees). Of course, I can > add +360 and find a crude value of -110.91 . Please, could you give some > advise if this is correct? > > Thank you in advance > > My best wishes > > Eduardo> https://clicktime.symantec.com/a/1/KFcoT6n7_A2GT5R2V8X8ljFSw7crS__S__rkKWoQfRU=?d=p7qftUdrzzirEMPcDGslD_ks0GFL4UTg4m88irG23_0whuaExYWFM61UZNqiJn19yRUc-6Yldj8AhLlLpZUHBPuFlJGKGSV1qkX_7eT_iQUj8S_GXmkSXdxiyTukwX336m47_4KBxazYpbrgTLIpqz2X0ySvcL4Q55QgPFZo1lh9oRHb0e7gS8qolswGyfjQs--NGHBlqulMOsvCXx7i_KGdRcmm6QLSOzrmp0ih5IJCewQPFOqAqHahYhTnPHzp-LQyv_7EZul2ATWT2vnDHgrClLTxjqaubB2xkJbTZoaKiBf0hnxWaJEyLnnWZ3NE3kDiBI2BlW7LsrczDlKKEdkIX1u7UfbQL9vu9fohVy-8o5F6Hw10Bp1nF9MdhifgTUo2dv_fRgoSQf71kasRSxqN-SQb6vcKRRcWzJKVFm8UcwUIQxG8Mb7B_IV4He0JXvL-YdEF7x1tzdvaIko%3D&u=http%3A%2F%2Fwww.ccl.net%2Fcgi-bin%2Fccl%2Fsend_ccl_message> 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If you have received this message in error, please notify us and remove it from your system and note that you must not copy, distribute or take any action in reliance on it. Any unauthorized use or disclosure of the contents of this message is not permitted and may be unlawful. From owner-chemistry@ccl.net Thu Sep 20 10:18:00 2018 From: "Rzepa, Henry S h.rzepa(~)imperial.ac.uk" To: CCL Subject: CCL: Strange value for Optical Rotation in g09 Message-Id: <-53470-180920045639-10635-zx+w+ZUe5URv62Rqd1oWAg]-[server.ccl.net> X-Original-From: "Rzepa, Henry S" Content-ID: <7AF23B09AE92494FA2DE74AD0D93BFD8]-[eurprd06.prod.outlook.com> Content-Language: en-US Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="us-ascii" Date: Thu, 20 Sep 2018 08:56:28 +0000 MIME-Version: 1.0 Sent to CCL by: "Rzepa, Henry S" [h.rzepa++imperial.ac.uk] I presume you calculated the optical rotation at 590nm (the sodium D line)? If there is a strong absorption in the UV/vis spectrum close by, the optical rotation may well suffer a sign inversion, or a very steep change in value with change in wavelength. So I suspect your compound must be coloured? Normally lamba (max) for optical transitions calculated using TD-DFT methods is also out by 15-25 nm, so the rotation for compounds absorbing in the 590nm region becomes even more difficult to predict accurately. Because of this phenomenon, optical rotations of > 100,000 degrees can often be measured and calculated! And remember that for large rotations you need to dilute the samples until the rotation is stable. Sometimes 10-6 or even 10-7M concentrations might be necessary. Oh, optical rotations are also quite sensitive to the DFT method used. And of course they can be ultra sensitive to conformations, particularly of phenyl groups. > > >> On 19 Sep 2018, at 23:39, Eduardo Lemos de Sa edulsa%%ufpr.br wrote: >> >> >> Sent to CCL by: "Eduardo Lemos de Sa" [edulsa**ufpr.br] >> Dear >> >> I have performed calculations on g09 aiming to determine optical rotation >> values for some organic molecules. Almost results are fine (apparently) >> but, one of them pointed me a value of -470.91 (degrees). Of course, I can >> add +360 and find a crude value of -110.91 . Please, could you give some >> advise if this is correct? >> >> Thank you in advance >> >> My best wishes >> >> Eduardo >> >