From owner-chemistry@ccl.net Thu May 11 16:07:01 2023 From: "Partha Sengupta anapspsmo*_*gmail.com" To: CCL Subject: CCL: hydrogen bond Message-Id: <-54917-230511155017-1595-4uPjc7eEDbVpXaqBgAn7tw]*[server.ccl.net> X-Original-From: Partha Sengupta Content-Type: multipart/alternative; boundary="00000000000087fb0705fb704b3a" Date: Fri, 12 May 2023 01:19:53 +0530 MIME-Version: 1.0 Sent to CCL by: Partha Sengupta [anapspsmo]_[gmail.com] --00000000000087fb0705fb704b3a Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sir, please send me your email address. Partha On Sat, 6 May 2023, 10:21 Kurten, Theo C theo.kurten]=3D[helsinki.fi, < owner-chemistry||ccl.net> wrote: > Dear Partha, > > > > are you familiar with the IUPAC definition of a hydrogen bond? E.g. here: > > > > http://publications.iupac.org/pac/pdf/2011/pdf/8308x1637.pdf > > > > Based on that, it=E2=80=99s clear that there is indeed a POSSIBILITY of a= H-bond, > as you have a potential H-bond donor (N-H) and two possible acceptors (th= e > N atoms, and the pi-electron system). However, it also seems likely that > the interaction will be quite weak, to the point of the existence of a > H-bond being a borderline case, likely depending on the conditions (see t= he > footnotes in the linked pdf). > > > > Some quick-and-dirty calculations on my laptop (using Spartan =E2=80=9920= , wB97xD > and a 6-31+G(d) basis set set - and yes I know there are better basis set= s > available but this should be good enough for the present purpose) confirm > this: for the H-bond to the N atom, the distance is pretty large (H=E2=80= =A6N is > almost 2.4 =C3=85), the NHN angle is far from linear (about 129 degrees),= the > N-H bond length increase and vibrational redshift (compared to isolated > methyl amine) are on the order of 0.002 =C3=85 and a few wavenumbers, > respectively, and interaction energy is only about 20 kJ/mol (of which a = lot, > possibly even most, is probably just basis set superposition error due to > my small basis set). > > > > For the H-bond to the pi-system, the distance (to the center of the ring) > is even longer (almost 2.6 =C3=85), the interaction energy is even lower = (about > 10 kJ/mol), the N-H bond length is identical (to 0.001 =C3=85) to isolate= d > methyl amine, and the frequencies are actually blueshifted by a few cm-1 > (the latter may just be an artefact though). So this is likely not a > H-bond at all, as per the IUPAC definition > > > > Whether or not you want to call the first interaction (from the methyl > amine NH to the pyrazine N) a H-bond really really depends on what you wa= nt > to do with this information. > > > > Best regards, > > Theo Kurt=C3=A9n > > (University of Helsinki, Finland) > > > > > > *From: *owner-chemistry+theo.kurten=3D=3Dhelsinki.fi__ccl.net > on behalf of Part= ha > Sengupta anapspsmo=3Dgmail.com > *Date: *Friday, 5. May 2023 at 17.15 > *To: *Kurten, Theo C > *Subject: *CCL: hydrogen bond > > I am not interested in ChatGpt. I ask the question to be answered from a > chemical point of view. I repeat the question again" Is there any > possibility between the hydrogen bond formation between pyrazine and meth= yl > amine". If there is any chance please give me the references. > > Partha > > > > > > -- > > > > *Dr. Partha Sarathi Sengupta Associate Professor Vivekananda > Mahavidyalaya, Burdwan* > --00000000000087fb0705fb704b3a Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Sir, please send me your email address.=C2=A0 Partha
On Sa= t, 6 May 2023, 10:21 Kurten, Theo C theo.kurten]=3D[helsinki.fi, <own= er-chemistry||ccl.net> wrote:

Dear Partha,<= u>

=C2=A0

are you familiar with the IUPAC defini= tion of a hydrogen bond? E.g. here:=C2=A0

=C2=A0

htt= p://publications.iupac.org/pac/pdf/2011/pdf/8308x1637.pdf=

=C2=A0

Based on that, it=E2=80=99s clear that= there is indeed a POSSIBILITY of a H-bond, as you have a potential H-bond = donor (N-H) and two possible acceptors (the N atoms, and the pi-electron sy= stem). However, it also seems likely that the interaction will be quite weak, to the point of the existence of a H-bond being a borderlin= e case, likely depending on the conditions (see the footnotes in the linked= pdf).=C2=A0

=C2=A0

Some quick-and-dirty calculations on m= y laptop (using Spartan =E2=80=9920, wB97xD and a 6-31+G(d) basis set set -= and yes I know there are better basis sets available but this should be good enough for the presen= t purpose) confirm this: for the H-bond to the N atom, the distance = is pretty large (H=E2=80=A6N is almost 2.4 =C3=85), the NHN angle is far fr= om linear (about 129 degrees), the N-H bond length increase and vibrational redshift (compared to isolated methyl amine) are = on the order of 0.002 =C3=85 and a few wavenumb= ers, respectively, and interaction energy is only about 20 kJ/mol (of which= a lot, possibly even most, is probably just basis set superposition error due to my smal= l basis set).=C2= =A0

=C2=A0

For the H-bond to the pi-system, the d= istance (to the center of the ring) is even longer (almost 2.6 =C3=85), the= interaction energy is even lower (about 10 kJ/mol), the N-H bond length is= identical (to 0.001 =C3=85) to isolated methyl amine, and= the frequencies are actually blueshifted by a = few cm-1 (the latter may just be an artefact th= ough). So this is likely not a H-bond at all, as per the IUPAC definition

=C2=A0

Whether or not you want to call the fi= rst interaction (from the methyl amine NH to the pyrazine N) a H-bond reall= y really depends on what you want to do with this information.

=C2=A0

Best regards,

Theo Kurt=C3=A9n

(University of Helsinki, Finland)

=C2=A0

=C2=A0

From: owner-chemistry+the= o.kurten=3D=3Dhelsinki.fi__ccl.net <owner-chemistry+theo.kurten=3D= =3Dhelsinki.fi__ccl.net> on behalf of Partha Sengupta anapspsmo=3D= gmail.com= <owner-chemistry__ccl.net>
Date: Friday, 5. May 2023 at 17.15
To: Kurten, Theo C <theo.kurten__helsinki.fi>
Subject: CCL: hydrogen bond

I am not interested= in ChatGpt. I ask the question to be answered from a chemical point of vie= w.=C2=A0I repeat the question again" Is there any possibility between = the hydrogen bond formation between pyrazine and methyl amine". If there is any chance please give me the references.<= u>

Partha

=C2=A0

=C2=A0

--

Dr= . Partha Sarathi Sengupta
Associate Professor
Vivekananda Mahavidyalaya, Burdwan

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