21
votes
Accepted
Why is the boiling point of stibane higher than that of ammonia?
Though it does go against your intuition, you've actually mentioned the answer in your question. Stibane has a higher boiling point than ammonia/azane on account of van der Waals interactions (owing ...
- 18.8k
18
votes
Do symmetric hydrogen bonds in neutral molecules exist?
This question crossed my mind during a lab today because we were making $\ce{Ni(dmg)2}$, which is shown below.
Well first, this is charged in some sense, but it is net-neutral. Also, the ...
- 13.1k
15
votes
Accepted
How to identify hydrogen bonds and other non-covalent interactions from structure considerations?
It is safe to say that there will always be intermolecular forces at play. At the time where you will consider these you should already have a good idea about the molecules involved in your system.
...
- 44.3k
13
votes
Is there intramolecular hydrogen bonding in salicylaldehyde?
It can indeed hydrogen bond, this can (to a certain extent) be observed by NMR. Due to the internal hydrogen bonding, the phenolic proton is surprisingly consistent, and shows no dependence on ...
- 17.2k
13
votes
Solubility of ortho- and para-nitrophenol in benzene
It turns out that the opposite of what happens in polar solvents takes place when a non-polar solvent is used. At the same temperature, o-nitrophenol is more soluble in benzene than it's m and p ...
- 6,278
13
votes
Accepted
Does ammonia exhibit hydrogen bonding in its gaseous state?
The paper[1] referenced by Nilay Ghosh says that,
it is well known that hydrogen bonds commonly exist in ammonia clusters and play an important role
and gives a picture of some of the clusters that ...
- 14.1k
13
votes
Why does potassium bifluoride exist whereas bichloride does not?
The bichloride ion $\ce{HCl2^-}$ does exist, but it requires other environment than usual solutions in water. E.g. solution of $\ce{[N(CH3)4]Cl}$ salt and undissociated $\ce{HCl(solv)}$ in ...
- 42.7k
11
votes
Accepted
Are there any other elements that get less dense in their solid state?
Your terminology is a little off: water isn't an element.
There isn't really a simple single explanation of why some solids are less dense than their associated liquids. The general explanation (which ...
- 37k
11
votes
Accepted
Which dicarboxylic acid has the most acidic hydrogen?
The $\mathrm pK_\mathrm a$ of the $\ce{CH2}$ group in a dicarbonyl compound is roughly $10$, whereas the $\mathrm pK_\mathrm a$ of a carboxylic acid is roughly $5$. For example, dimethyl malonate has ...
- 71.6k
11
votes
Do symmetric hydrogen bonds in neutral molecules exist?
In Schaefer's paper,[1] which you linked, the authors describe nitromalonamide as being the compound with the lowest calculated barrier to intramolecular proton transfer, or tautomerisation.
Earlier ...
- 71.6k
11
votes
Accepted
Why can't alcohols form hydrogen-bonded dimers like carboxylic acids?
The strength of a hydrogen bond somewhat depends on the $\ce{X-H\bond{...}X}$ angle that the hydrogen-bonding hydrogen forms with the two electronegative elements $\ce{X}$. In our case, carboxylic ...
- 68.4k
11
votes
Is a temperature decrease required for hydrogen bonds to form in water?
You are right, in a sense.
A more accurate statement would be that as the temperature decreases, the average lifetime of a hydrogen bond increases. Thus, on average the liquid/solid/molecule will be ...
- 13.1k
11
votes
Accepted
Why hydrogen bonding in some acids make them a stronger acid when it is present even before deprotonation?
Some of the conformers of salicylic acid are given below, all of which are planar in configuration.$\mathrm{^{[1]}}$
Although the compound can adopt several conformations the first conformer(in the ...
- 477
10
votes
Accepted
Why isn't Indigo soluble in water?
True, Indigo can form hydrogen bonds, but with what? Is it water? Nope.
It makes hydrogen bonds with itself.
This makes the molecule incapable of bonding with water. Not only that, but the molecule ...
10
votes
Accepted
Do amines or alcohols have stronger intermolecular hydrogen bonds?
The boiling point of non-ionic compounds are highly depend on their H-bonding abilities. For example, boiling point of water (molar mass: $\pu{18.02 g/mol}$) is $\pu{100 ^\circ C}$ at $\pu{1 atm}$ ...
10
votes
Do amines or alcohols have stronger intermolecular hydrogen bonds?
Mathew Mahindaratne has provided analysis based on experimental values of the boiling points of the two compounds. I would like to offer a different view using bonding analysis.
Before I begin ...
- 10.7k
9
votes
Accepted
Hydrogen bonding in staggered vs eclipsed conformations
Disclaimer: I am not a computational chemist, I am completely new to this stuff. Just a humble student of @pentavalentcarbon
However, my thought is that if you have interacting OH groups, the ...
- 8,495
9
votes
Boiling points of Butan-2-ol and Butan-1-ol
You have certainly understood the main idea.
In general the boiling point of a substance is determined by the way the molecules come together. The closer they are, the bigger are the intermolecular ...
- 1,033
9
votes
Accepted
What is a hydrogen bond acceptor and donor?
Dissenter's answer which you linked appears to be wrong (as of now). I have left a comment.
The conventional way in which we talk about hydrogen bond acceptors/donors is: in a hydrogen bond $\ce{X-H.....
- 71.6k
8
votes
Accepted
Why do Asn-Ser and Gln-Thr have different H bonding patterns?
I don't have the textbook you've gotten this from, but unless there's a statement to the contrary, I suspect these are intended as examples of hydrogen bonding, rather than an exhaustive list of the ...
- 4,982
8
votes
Accepted
IChO problem involving the condensation point of NF3, NHF2, NH2F
The interactions do not limit to only dipole-dipole, which means positive charge is not everything.
What's special about $\ce{NF3}$? It has no hydrogens. As a result, it cannot form hydrogen bond, ...
- 498
8
votes
Accepted
Which is more soluble in water, HF or SO2?
There are a couple different forces at play here. One big difference between the compounds is that $\ce{SO2}$ is much more volatile, with a boiling point of $\pu{-10 ^\circ C}$; in other words it's a ...
- 17.6k
8
votes
Accepted
Can =NH2+ in Arginine's side chain form hydrogen bonding at physiological pH?
Yes, the arginine side chain is an excellent hydrogen bond donor. Charged N-H groups are even better hydrogen bond donors than the corresponding neutral N-H groups. Here is an article that gives ...
- 41.2k
8
votes
Accepted
Solubility of ortho- and para-nitrophenol in benzene
The nitrophenols have completely different physical behavior based on the position of nitro group:
$$
\begin{array}{c|ccc}
\hline
\text{Compound} & \text{Melting point} & \text{Boiling point} ...
8
votes
Why does potassium bifluoride exist whereas bichloride does not?
The bichloride ion, including isolated salts, has in fact been known since 1954 [1]; but it appears to require relatively bulky counterions whereas bifluoride has a broader range of stable salts.
To ...
- 60k
7
votes
Which intermolecular interaction is dependent on the inverse cube of distance?
2
The ion-ion or charge-charge interaction is given by
$$
V_{\text{cc}} = \frac{Z_{i}Z_{j}e^{2}}{4\pi\epsilon_{0}} \frac{1}{|\mathbf{R}_{i} - \mathbf{R}_{j}|}
$$
and is therefore proportional to $R^...
- 7,499
7
votes
Explain volume contraction in mixtures of alcohol and water
Liquid water can be thought of as having an average configuration that tends to be an open, almost crystalline structure, somewhat like that for hexagonal ice crystals $\mathrm{^{[1,2,3]}}$. This ...
- 17.6k
7
votes
Accepted
Hydrogen Bond Without Hydrogen
Just looking at the electronegativities, there seems to be no reason why atoms such as boron, carbon or silicium — which all have similar electronegativities to hydrogen — should not undergo hydrogen-...
- 68.4k
7
votes
Accepted
Does fumaric acid form stronger hydrogen bonds than maleic acid?
Intramolecular hydrogen bonds do not have to be weak, but the strength of a hydrogen bond depends a lot on the $\ce{O-H\bond{....}O}$ angle. With intramolecular hydrogen bonds, it is often hard to ...
- 68.4k
7
votes
Why is ice less dense than water?
The following is an image of the hexagonal crystaline form of ordinary ice (Ice I$_h$) taken from S.S. Zumdahl, Chemistry, 3rd ed., copyright © 1993 by D.C. Heath and Company:
Note that the ...
- 17.6k
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