PH3 Permanent Dipole

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TheTennisOne
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#1
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#1
Does PH3 exhibit permanent dipole-dipole, and if so - why?
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monkeyman0121
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I do not think so. I think P-H bonds are non-polar. I think they can only form very weak hydrogen bonding.
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TheTennisOne
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Bump ^ that doesn't help
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charco
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(Original post by TheTennisOne)
Bump ^ that doesn't help
P & H have the same electronegativity so the actual P-H bonds are not dipoles:
http://www.thecatalyst.org/electabl.html

It's b.p is -88ºC (Mr = 34)

This compares with ethane, C2H6, b.p -88.5ºC (Mr = 30)

This is empirical evidence of lack of polarity.
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TheTennisOne
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(Original post by charco)
P & H have the same electronegativity so the actual P-H bonds are not dipoles:
http://www.thecatalyst.org/electabl.html

It's b.p is -88ºC (Mr = 34)

This compares with ethane, C2H6, b.p -88.5ºC (Mr = 30)

This is empirical evidence of lack of polarity.
http://www.ocr.org.uk/Images/176054-...roups-june.pdf

http://www.ocr.org.uk/Images/175439-...and-groups.pdf

Question 3 d - states it does have permanent dipole though?
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alow
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(Original post by TheTennisOne)
http://www.ocr.org.uk/Images/176054-...roups-june.pdf

http://www.ocr.org.uk/Images/175439-...and-groups.pdf

Question 3 d - states it does have permanent dipole though?
From a symmetry argument you can show that phosphine would be expected to have a nonzero dipole moment (and it does, of 0.58D).
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Infraspecies
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The electron distribution isn't spherically symmetric.
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alow
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(Original post by Infraspecies)
The electron distribution isn't spherically symmetric.
Which is irrelevant. Not having spherical symmetry cannot tell you whether a molecule has a dipole or not.
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Infraspecies
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(Original post by alow)
Which is irrelevant. Not having spherical symmetry cannot tell you whether a molecule has a dipole or not.
I don't believe I stated that a non-spherical symmetry of the electron distribution was a necessary and sufficient condition for the existence of a dipole, I was being relatively vague to give him/her a reason to consider the symmetry implications of the molecule; something they may well not have thought on.
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alow
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#10
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(Original post by Infraspecies)
I don't believe I stated that a non-spherical symmetry of the electron distribution was a necessary and sufficient condition for the existence of a dipole, I was being relatively vague to give him/her a reason to consider the symmetry implications of the molecule; something they may well not have thought on.
Stating irrelevant facts isn't "being vague".

Jump down my throat if you like though, I've not had anyone in there for a while and the gonorrhea might get lonely.
What on Earth are you on about?
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Infraspecies
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#11
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(Original post by alow)
Stating irrelevant facts isn't "being vague".

What on Earth are you on about?
I mean you're right, I definitely misused the word 'spherically symmetric' as opposed to 'centrosymmetric sort of with more caveats about MO residency and organisation', so I suppose I thank you for pointing that out. It's been too long since doing it that the terms get all fuzzy and the wine definitely doesn't help.

As for the gonorrhea comment I guess I just bridled at how stiff and self-important you sound.
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TheTennisOne
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#12
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#12
Erm, so it does have a little bit of permanent dipole? Because the electron distribution isn't symmetrical cos of the lone pairs or?
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charco
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#13
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#13
(Original post by alow)
From a symmetry argument you can show that phosphine would be expected to have a nonzero dipole moment (and it does, of 0.58D).
Yes, the trigonal pyramidal shape does imply a non-zero dipole.
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