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Topic: Finding net dipole moments in 3D structures  (Read 2598 times)

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Offline confusedstud

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Finding net dipole moments in 3D structures
« on: February 20, 2013, 07:31:33 AM »
How can I visualize the net dipole moment in 3D structures? For example, in CH4 , it is deemed non polar. However, I don't quite 'see' it. The pyramidal base has a dipole moment acting upwards and the top of it where there is a C-H bond, it acts downwards. So it cancels out and has no net dipole moment.

I am unable to understand how they cancel out. So for a lot of 3D structures like CH3 CH2 CH3 or CH3 CF2 CH3 I can't really tell by myself about their net dipole moments. I would have to google it.

Can someone enlighten me? Thanks  :)

Offline sjb

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Re: Finding net dipole moments in 3D structures
« Reply #1 on: February 20, 2013, 09:51:24 AM »
How can I visualize the net dipole moment in 3D structures? For example, in CH4 , it is deemed non polar. However, I don't quite 'see' it. The pyramidal base has a dipole moment acting upwards and the top of it where there is a C-H bond, it acts downwards. So it cancels out and has no net dipole moment.

I am unable to understand how they cancel out. So for a lot of 3D structures like CH3 CH2 CH3 or CH3 CF2 CH3 I can't really tell by myself about their net dipole moments. I would have to google it.

Can someone enlighten me? Thanks  :)

Are you comfortable with resolving forces or other applied maths like mechanics?

Offline confusedstud

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Re: Finding net dipole moments in 3D structures
« Reply #2 on: February 20, 2013, 10:49:22 AM »
I have only resolved forces in 2 dimensions in my physics class. Or do we usually learn how to resolve forces or other vector quantities in 3 dimensions before learning about this?

Thanks :)

Offline sjb

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Re: Finding net dipole moments in 3D structures
« Reply #3 on: February 22, 2013, 02:43:08 AM »
Usually is perhaps a difficult question to answer, as different places have different syllabuses. However, perhaps try it and see if that helps. It's just an extension of 2-d resolution, after all.

Offline confusedstud

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Re: Finding net dipole moments in 3D structures
« Reply #4 on: February 22, 2013, 07:08:15 AM »
I can't really do it for long molecules like CH3CF2CH3 because that's when everything gets more confusing. How would students actually visualize them because I really can't.. It's like in CH4 i know it's non polar from the textbook I'm reading. However, I can't really explain it because if i look at the pyramidal structure CH3, its supposed to be equal to the C-H on the top which i can't visualize. But if i look at the sides of it like breaking it into 2 Vs then it makes more sense. But then again I can use that in the longer molecules so I'm pretty confused.

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