From chemistry-request %-% at %-% server.ccl.net Thu Mar 27 09:33:51 2003 Received: from srvus010.unitedcatalysts.com ([208.23.162.8]) by server.ccl.net (8.11.6/8.11.0) with SMTP id h2REXpe00627 for ; Thu, 27 Mar 2003 09:33:51 -0500 Received: by lvlxch02.unitedcatalysts.com with Internet Mail Service (5.5.2653.19) id ; Thu, 27 Mar 2003 09:32:17 -0500 Message-ID: <5CF08BBFE6DE97478C1E76E654CAF9089C25DA -x- at -x- lvlxch02.unitedcatalysts.com> From: "Shobe, Dave" To: "'Jinsong Zhao'" , "'CCL'" Subject: RE: How to calculate the bond energy Date: Thu, 27 Mar 2003 09:32:16 -0500 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: multipart/mixed; boundary="----=_NextPartTM-000-e746a0d4-8e84-4912-873c-a8be994bd814" This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------=_NextPartTM-000-e746a0d4-8e84-4912-873c-a8be994bd814 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C2F46D.AA2C2E70" ------_=_NextPart_001_01C2F46D.AA2C2E70 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable The usual definition of a bond energy is the energy requirement to = break that particular, bond. Actually, people are more likely to use the = enthalpy than the energy itself, and the result is often abbreviated BDE =3D = bond dissociation enthalpy. Using methylamine as an example, we have: BDE(C-H) =3D delta H for CH3NH2 --> H + CH2NH2 BDE(N-H) =3D delta H for CH3NH2 --> H + CH3NH BDE(C-N) =3D delta H for CH3NH2 --> CH3 + NH2 However if you add up all these BDEs you will find that they do not add = up to the atomization enthalpy of the molecule!! (i.e. delta H for CH3NH2 = --> C + N + 5 H) Defining a particular bond's contribution to the total = binding energy of the molecule is difficult, and I'm not aware of any standard definition. --David Shobe S=FCd-Chemie Inc. phone (502) 634-7409 fax (502) 634-7724 email dshobe (+ at +) sud-chemieinc.com Don't bother flaming me: I'm behind a firewall. =09 -----Original Message----- From: Jinsong Zhao [mailto:zh_jinsong-: at :-yahoo.com.cn] Sent: Thursday, March 27, 2003 1:34 AM To: CCL Subject: CCL:How to calculate the bond energy Dear all, I hope to calculate the energy of each bond in a organic compound. I am not familiar with quantum or computational chemistry. Would you like to give me some advice on this aspect? Thank you very much in advance! Sincerely yours, Jinsong Zhao _________________________________________________________ Do You Yahoo!?=20 =D1=C5=BB=A2=CD=A8=CD=F8=C2=E7KTV, = =CB=E6=CA=B1=CB=E6=B5=D8=C3=E2=B7=D1=BF=A8=C0=ADOK~~ http://rd.yahoo.com/mail_cn/tag/?http://cn.messenger.yahoo.com//chat/ind= ex.h tml -=3D This is automatically added to each message by mailing script =3D- CHEMISTRY -x- at -x- ccl.net -- To Everybody | CHEMISTRY-REQUEST -x- at -x- ccl.net -- To = Admins Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: = jkl-: at :-ccl.net ------_=_NextPart_001_01C2F46D.AA2C2E70 Content-Type: text/html; charset="gb2312" Content-Transfer-Encoding: quoted-printable RE: How to calculate the bond energy

The usual definition of a bond energy is the energy = requirement to break that particular, bond.  Actually, people are = more likely to use the enthalpy than the energy itself, and the result = is often abbreviated BDE =3D bond dissociation enthalpy.  Using = methylamine as an example, we have:

BDE(C-H) =3D delta H for CH3NH2 --> H + = CH2NH2
BDE(N-H) =3D delta H for CH3NH2 --> H + = CH3NH
BDE(C-N) =3D delta H for CH3NH2 --> CH3 + = NH2

However if you add up all these BDEs you will find = that they do not add up to the atomization enthalpy of the molecule!! = (i.e. delta H for CH3NH2 --> C + N + 5 H)  Defining a = particular bond's contribution to the total binding energy of the = molecule is difficult, and I'm not aware of any standard = definition.

--David Shobe
S=FCd-Chemie Inc.
phone (502) 634-7409
fax     (502) 634-7724
email  dshobe(-(at)-)sud-chemieinc.com

Don't bother flaming me: I'm behind a = firewall.

       =20

-----Original Message-----
From: Jinsong Zhao [mailto:zh_jinsong { *at * } yahoo.com.cn]
Sent: Thursday, March 27, 2003 1:34 AM
To: CCL
Subject: CCL:How to calculate the bond energy


Dear all,

I hope to calculate the energy of each bond in = a
organic compound. I am not familiar with = quantum  or
computational chemistry. Would you like to give = me
some advice on this aspect? Thank you very much = in
advance!

Sincerely yours,
Jinsong Zhao


_________________________________________________________
Do You Yahoo!?
=D1=C5=BB=A2=CD=A8=CD=F8=C2=E7KTV, = =CB=E6=CA=B1=CB=E6=B5=D8=C3=E2=B7=D1=BF=A8=C0=ADOK~~
http://rd.yahoo.com/mail_cn/tag/?http://cn.messenger.y= ahoo.com//chat/index.html


-=3D This is automatically added to each message by = mailing script =3D-
CHEMISTRY { *at * } ccl.net -- To Everybody  | = CHEMISTRY-REQUEST' at \`ccl.net -- To Admins
Ftp: ftp.ccl.net  |  WWW: http://www.ccl.net/chemistry/   | Jan: = jkl - at - ccl.net




------_=_NextPart_001_01C2F46D.AA2C2E70-- ------=_NextPartTM-000-e746a0d4-8e84-4912-873c-a8be994bd814--