H2S Hydrogen Bonding?

[DocDrakeRamoray]

I was watching The Gold Standard CD lectures and the guy said that H2S (Hydrogen sulfide) is able to hydrogen bond since Sulfide is in the same group as oxygen and Sulfide is highly electronegative.

I thought H2S was a gas and is not able to hydrogen bond?



I know that hydrogen attached to O,F, N can hydrogen bond, but never heard of H2S being able to form those kind of bonds.

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[TooMuchResearch]

I was watching The Gold Standard CD lectures and the guy said that H2S (Hydrogen sulfide) is able to hydrogen bond since Sulfide is in the same group as oxygen and Sulfide is highly electronegative.

I thought H2S was a gas and is not able to hydrogen bond?



I know that hydrogen attached to O,F, N can hydrogen bond, but never heard of H2S being able to form those kind of bonds.

You are correct. In fact, the only reason water is a liquid at room temperature while hydrogen sulfide, which has similar bonding and a higher molecular weight than water, is a gas is because water can hydrogen bond and hydrogen sulfide cannot.

 

[Naijaba]

The electronegativity of Nitrogen is 3.04 whereas the electronegativity of Sulfur is 2.58. Thus it's a matter of degree. For the MCAT, I would assume only N, O, and F can hydrogen bond.

 

[sleepy425]

H-S bonds exhibit weaker hydrogen bonding than H-O, H-N, or H-F bonds (which is why H2S is a gas at RT but water is not), but that doesn't mean they do not hydrogen bond. As Naijaba said, it's a matter of degree. Hydrogen bonding involving H-S hydrogen bond donors and S hydrogen bond acceptors also happen to have different optical geometric orientations (I'm not sure exactly what it is, but it's not 180 degrees like with the strong hydrogen bond donors and acceptors). The point is, you need to realize that hydrogen bonding isn't some magical thing that all of a sudden happens with O, N, or F. It involves the same electrostatic properties that give us dipole-dipole effects among others, but it's just a term used to describe particularly strong dipole-dipole interactions that occur when two electronegative atoms are bridged by a hydrogen. I feel like the way it is commonly taught makes it seem like it is a different phenomenon, but it's really the same thing.

 

[loveoforganic]

But it's only useful to define it differently when the effects from it are substantially different from those expected, which is why the definition is taught as it is. Sure, H2S is forming an H-S-H-S bond network, but that network is so weak it's not really worth differentiating between normal dipole-dipole interactions unless you're a p-chemist.

 

[sleepy425]

But it's only useful to define it differently when the effects from it are substantially different from those expected, which is why the definition is taught as it is. Sure, H2S is forming an H-S-H-S bond network, but that network is so weak it's not really worth differentiating between normal dipole-dipole interactions unless you're a p-chemist.

well, yes, I agree that that is why they teach it that way. however, the effects are not substantially different from what is expected. in fact, they are exactly what is expected. as you increase the electronegativity of the heteroatom, the dipole-dipole interaction becomes stronger.

I wasn't saying that I disagree with defining certain interactions as "hydrogen bonding." I just think that most students leave their chemistry classes thinking that it is something completely different from dipole-dipole interactions, which it is not. And there are many interactions other than those involving O, N, or F that are considered to be hydrogen bonding. It's just that, the traditional O-H, N-H, and F-H hydrogen bonds are classified as strong hydrogen bonds, and other types are called weak hydrogen bonds (there's even a book called "The Weak Hydrogen Bond," which is really interesting).