hybridization sp4
cpajr
Hello fiends! my name is Cláudio Júnior and I am chemistry teacher and
today I'll like informations about hybridization sp4.write to me.
my e-mail is cp...@elogica.com.br
cpajr
hello! fiends. I'll like informations about hybridization sp4 .Please
help me!
my e-mail is cp...@elogica.com.br
Alan M
Senor Junior,
You are asking for a *lot* of information and this is not the place to
get it. Any decent library found at most universities and big cities
worldwide (what is br?) will carry books on organic chemistry. Many
popular texts have been translated into dozens of languages.
hybridization (linear combination of atomic orbitals) is generally
featured in these texts.
Alan
--
Alan W. Messing, Ph.D.
Director Otro gallo nos cantara
Applied Marine Research Laboratory
Old Dominion University
Norfolk, VA 23529
Eric Lucas
Caveat 1: What I'm about to say assumes you understand more "usual"
hybridizations like sp3--i.e., that describing hybridization of a carbon
bearing only single bonds. Caveat 2: I'm not a theoretician, just a
practicing organic chemist to whom hybridization is not a rigorous
concept, but rather merely a heuristic to help understand structure,
property and reactivity patterns.
In a quick word...: (yeah, you all know I've never said a quick word in
my life....)
In some molecular structures, something about the structure demands
certain orbitals have less than full contribution from the s orbital to
certain bonding hybrids. For example, in cyclopropane, the highly
strained bonds in the ring require orbitals that have a greater radial
extent toward the other atoms. Since the s orbital has a maximum at the
nucleus and the p orbital has greater radial extension, the way to do
this is reduce s contribution and increase p contribution in the ring
bonds. By decreasing the s content in the ring bonds, the bonding
orbitals extend toward the other atoms in the ring better, giving better
overlap and forming stronger bonds. A better description is probably an
orbital which is a linear combination having 3/4 contribution of the s
orbital and full contribution from all 3 p orbitals. Rather than
writing s(3/4)p3, it's more common to write sp4, even though there
aren't 4 different p orbitals that contribute to the hybrid. The upshot
of this, for example in cyclopropane, is that the remaining orbitals
(the ones that form exocyclic bonds) have greater *s* character (to
balance the less-than-complete contribution of the s orbital to the ring
bonds.)
These changes in hybridization from sp3 lead to the expected changes in
reactivity in the molecule. Because of the increased p character in the
ring bonds, reactivity in some cases approaches that of olefins. For
example, I believe you can chlorinate cyclopropane under non-radical
conditions, to 1,3-chlorobutane. And acids can open the ring in the
same way that they can open a C=C double bond. And the C-C bonds in the
ring can enter into a sort of conjugation with orbitals alpha to the
ring (radicals, anions and cations), in the same way that double bonds
stabilize allylic orbitals (radicals, anions, cations). On the other
hand, because of the greater s character in the exocyclic bonds of
cyclopropane, the NMR shifts of any attached Hs are generally way
upfield. And halogens on the ring can undergo rapid, clean
metal-halogen exchange similar to other sp2 halides (vinylic, aromatic).
However, you should follow Alan's advice and find a good book on the
subject. As far as I know, any advanced undergraduate or graduate
physical organic text will address the issue.
Eric Lucas
Eric Lucas
Hate to follow up my own post, but this brings up a question that I knew
noone would have read at the end of that last tome....
Anyone ever read anything on the mechanism of cyclopropane acting as an
anaesthetic? Seems kinda anamolous to me. Of course, I guess I have to
admit I don't know how chloroform or ether function either.
Eric Lucas
Eric Lucas wrote:
[big snip about cyclopropane]
Uncle Al
Eric Lucas wrote:
>
> Hate to follow up my own post, but this brings up a question that I knew
> noone would have read at the end of that last tome....
>
> Anyone ever read anything on the mechanism of cyclopropane acting as an
> anaesthetic? Seems kinda anamolous to me. Of course, I guess I have to
> admit I don't know how chloroform or ether function either.
Stuff that swells fatty acid bilayer membranes - xenon, nitrous oxide,
cyclopropane, nitrogen under pressure, organic solvents; halothane,
isoflurane... - is anesthetic. (I suppose there is a toxicity caveat.)
Stuff that thins said membranes - helium under pressure, perfluorinated
ethers - is convulsant.
(The curious correlation between subdermal silicone and breast
enlargement cannot be currently reproduced.)
--
Uncle Al Schwartz
Uncl...@ix.netcom.com ("zero" before @)
http://pw2.netcom.com/~uncleal0/uncleal.htm
http://www.ultra.net.au/~wisby/uncleal.htm
http://www.guyy.demon.co.uk/uncleal/uncleal.htm
(Toxic URLs! Unsafe for children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Alan M
Hey Eric,
I woke up in the middle of the night last night and thought "he said
sp4"! That is so foreign a phrase that I read it as sp3! And I
responded as I did for someone asking the question about sp3. I like
your explanation, but I dislike the concept of taking something as
useful as LCAO and screwing up the nomenclature. George Zweifel, my
small rings professor, called them banana bonds, characterized them as
strained and taught the lesson that anything under strain is reactive
and subject to relieving the strain in the most expedient manner
available. It also provides a partial explanation for recent school
yard shootings.
I shall try to be more attentive in the future (BTW, you meant either
methylcyclopropane or 1,3-dichloropropane above).
John Doe
In article <354CC1...@spamless.estuary.amrl.odu.edu>, Alan M
<ames...@spamless.estuary.amrl.odu.edu> wrote:
> > cpajr wrote:
> > >
> > > hello! fiends. I'll like informations about hybridization sp4 .Please
> > > help me!
> > > my e-mail is cp...@elogica.com.br
>
> Hey Eric,
>
> I woke up in the middle of the night last night and thought "he said
> sp4"!
Yeah. I think everyone who responded correctly ignored the original
poster's misprint.
I once say a picture of George Olah with CH5+ on the board behind him.
Is this an example of s2p3 bonding, since the fifth bond must(?) come from
the 1s electrons?
John
Eric Lucas
John Doe wrote:
>
> Yeah. I think everyone who responded correctly ignored the original
> poster's misprint.
Why do you assume it was a misprint, seeing it was repeated 4 times in
two different posts?
> I once say a picture of George Olah with CH5+ on the board behind him.
>
> Is this an example of s2p3 bonding, since the fifth bond must(?) come from
> the 1s electrons?
No, I believe it comes from protonation of a C-H bond, making that CHH
interaction a 3-center-2-electron bond involving only the valence shell
on C. A dihydrogen complex of the empty p-orbital of CH3+, for those
who are familiar with transition metal chemistry, analogous to a H2
complex of a d0 metal.
Eric Lucas
John Doe
In article <354CE2C1...@ix.netcom.com>, Eric Lucas
<eal...@ix.netcom.com> wrote:
> John Doe wrote:
> >
> > Yeah. I think everyone who responded correctly ignored the original
> > poster's misprint.
>
> Why do you assume it was a misprint, seeing it was repeated 4 times in
> two different posts?
>
>
Thanks for the answer to my CH5+ question
How many of those were spawned by quotes of the original? One mention was
a realization by another that sp4 had actually been printed rather than
sp3.
I assumed it was a misprint because that was the simlplest explanation.
Otherwise I'd be going off on the idea that sp4 exists. Should I do that?
"Entities ought not to be multiplied, except from necessity." William of Occam
John
Eric Lucas
John Doe wrote:
>
> I assumed it was a misprint because that was the simlplest explanation.
> Otherwise I'd be going off on the idea that sp4 exists. Should I do that?
Go ahead if you want. It's a perfectly accepted concept that explains
(rationalizes?) the chemistry of cyclopropanes. It's not really sp4,
but something like s(3/4)p3. In other words, an sp3 orbital somewhat
depleted in s content. Why do you have a problem with the existence of
such a beast?
Eric Lucas
John Doe
In article <354E5510...@ix.netcom.com>, Eric Lucas
<eal...@ix.netcom.com> wrote:
No problem. lack of knowledge in organic chemistry. Appreciate the help. Again.
I don't remember the full extent of your originl answer, but it does seem
that the thrust was aimed at an sp3 concept. Was the above discussed at
that time?
JD