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PH3 Permanent Dipole

Does PH3 exhibit permanent dipole-dipole, and if so - why?
I do not think so. I think P-H bonds are non-polar. I think they can only form very weak hydrogen bonding.
Bump ^ that doesn't help
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.
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-mark-scheme-unit-f321-atoms-bonds-and-groups-june.pdf

http://www.ocr.org.uk/Images/175439-question-paper-unit-f321-01-atoms-bonds-and-groups.pdf

Question 3 d - states it does have permanent dipole though?
Reply 5
Avatar for alow
alow
19
Original post by TheTennisOne


From a symmetry argument you can show that phosphine would be expected to have a nonzero dipole moment (and it does, of 0.58D).
The electron distribution isn't spherically symmetric.
Reply 7
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alow
19
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.
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.
(edited 6 years ago)
Reply 9
Avatar for alow
alow
19
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?
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.
Erm, so it does have a little bit of permanent dipole? Because the electron distribution isn't symmetrical cos of the lone pairs or?
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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