Comments on: Polar Protic? Polar Aprotic? Nonpolar? All About Solvents

By: KD

KD — Fri, 21 Jun 2024 06:55:51 +0000

Hey James,great post as expected from you.Just wanted to know,1)Is there any trend between the Dielectric constant and Dipole moment of an solvent,or does it just depends upon the structure of the molecules.2)Which is a better determining factor for polarity, dielectric constant or dipole moment?.Thanks for the help.

By: James Ashenhurst

James Ashenhurst — Tue, 29 Nov 2022 20:20:45 +0000

In reply to Alicia. We use a separatory funnel. Polar and non-polar solvents generally do not mix.

By: Alicia

Alicia — Tue, 29 Nov 2022 12:36:32 +0000

Yes,I mean how to physically separate them in labs Thanks

By: James Ashenhurst

James Ashenhurst — Tue, 29 Nov 2022 09:32:37 +0000

In reply to Alicia.

Do you mean separate as in physically separate them in the lab, or do you mean separate as in “distinguish” ?

Most important difference for distinguishing polar solvents: look for O-H bonds, because they will have hydrogen bonding (O is much more electronegative than H and there will be a large partial negative charge on oxygen and a large partial positive charge on hydrogen). Second most important difference: look for bonds where there is a large electronegativity difference, such as the C=O in acetone and DMF, S=O in DMSO, CN in acetonitrile.

Very nonpolar solvents (hydrocarbons) only have C-H bonds.

The key measurement to look for is something called “dielectric constant” which is large for polar molecules and small for non polar molecules.

By: Alicia

Alicia — Mon, 28 Nov 2022 21:30:55 +0000

24th of November 2022
How do you seperate polar solvents from non polar solvents

By: Arti

Arti — Tue, 14 Jul 2020 05:54:55 +0000

This is very helpful for clear understanding.. Thank u

By: James Ashenhurst

James Ashenhurst — Tue, 02 Jun 2020 15:24:06 +0000

In reply to Aryan Bhaskar. Great comment. Thank you very much. Should have thought of this.

By: Aryan Bhaskar

Aryan Bhaskar — Sun, 31 May 2020 10:18:02 +0000

Well, I guess I have something to contribute regarding the dipole moments of DCM and Chloroform. The thing is that the structure of both of these is tetrahedral with bond angle =cos-1(-0.33)=109.5 deg. Now, if you’ve got some idea about vectors, then you’ll realize that four vectors kept at this angle give net=0. But the very interesting thing is that the resultant of THREE such vectors is equal to ONE such vector, just in the opposite direction. So, in case of of chloroform, the THREE -Cl actually contribute to the dipole moment as if it were just ONE -Cl. However, in case of DCM, the TWO -Cl contribute as if there were 2cos(54.9deg.) -Cl = 1.15 -Cl

In summary, using a bit of vector algebra:
IN CHCl3 = Dipole eqv. to 1 -Cl
IN CH2Cl2 = Dipole eqv. to 1.15-Cl

By: James Ashenhurst

James Ashenhurst — Wed, 04 Dec 2019 19:11:14 +0000

In reply to JA. NHC?

By: JA

JA — Tue, 03 Dec 2019 19:14:24 +0000

Would a solvent with NH2 or NHC be worse?