Questions tagged [intermolecular-forces]
The forces, either attractive or repulsive, that exist between molecules due to electric charges or varying electron cloud distribution. This tag could also include intra-molecular attractions (within one molecule itself) often found in a protein amino acid residues.
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Why are Dispersion Interactions Stronger in Molecules with Bigger Molecular Mass? [duplicate]
Usually there are two explanations:
When dipoles are induced due to movement of electrons in the molecule, they are bigger in molecules with more mass since they have/include more atoms (has sense to ...
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Why does Ethylene Glycol have higher boiling point than Propylene Glycol?
Looking at the two alcohols, both have hydrogen bonding and are singly bonded throughout the molecule. However, propylene glycol has a larger electron cloud which to my knowledge would increase its ...
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Why do fluoride molecules seem to have abnormally low boiling points?
As far as I know, to non-polar molecules like CF4 and C2H6,
boiling point is mainly affected by the London dispersion force.
As a result, molecules with more protons and electrons normally have higher ...
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Which definition of van der Waals forces is correct? [duplicate]
I've been told by my teacher that van der Waals forces is the formal name for intermolecular forces. But on the internet, many people are saying van der Waals forces is another name for London ...
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What are the different types of van der Waals forces?
As per different websites on internet van der Waals force are of
Three types (Keesom force, Debye force and London dispersion force) @ Wikipedia
Two types (Dipole-dipole force/Keesome force and ...
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Why hydrogen bonds are stronger than Van der Waals forces?
Why the hydrogen bonds are more intense than Van der Waals forces in the case where the molecules with the Van der Waals forces have a stronger dipolar moment than the molecules with the hydrogen bond?...
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Why do bubbles form and stay when I shake a bottle of tea?
I have some bottled tea and I noticed that shaking it creates some foamy bubbles that stay for quite a while (at least half an hour if not more). I originally thought it has something to do with my ...
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Why does water weaken ion ion attractions?
My lecturer has told me that water, having a high dielectric value, will "shield" ions and reduce ion-ion attractions.
I really don't see why. Having water molecules surround these two ions ...
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How does intramolecular hydrogen bonding cause the molecules to be separated from each other?
I learnt about intramolecular hydrogen bonding today, which occurs between molecules such as ortho-nitrophenol. What I was told is that in case of intramolecular bonding, the molecules separate from ...
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Magnitude of Lennard-Jones force evaluated with molecular dynamics simulation
The intent is to evaluate the error source of a molecular dynamics (MD) simulation which is only based on the Lennard-Jones interaction between noble gases (helium in this case). What is the magnitude ...
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Why are steric effects repulsive?
Normally, I think about orbitals interacting in the context of bonding. When two atomic orbitals overlap, they can do so in-phase or out-of-phase. The in-phase overlap results in a bonding molecular ...
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What effect on boiling and melting points does intramolecular hydrogen bonding have? [duplicate]
I know that intermolecular forces increase the boiling and melting point of a compound, but what is the effect of intramolecular forces on boiling and melting points?
I found contradicting answers ...
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Help understanding how "steric effects" are distinct from "electronic effects"?
@jakebeal's excellent answer to Why do animal cells “mistake” rubidium ions for potassium ions? includes the following passage:
In the case of potassium versus sodium, which are both very important ...
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How are polarizabilities measured experimentally?
Most common spectroscopies that produce either a full spectrum, a tensor, or a scalar value have a specific instrument associated with them that is relatively self-contained and not custom. For ...
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Intermolecular forces of attraction between positional isomers of alcohols
This seemingly trivial question is as follows: Why is the boiling point of 1-butanol ($\ce {117.7 ^\circ C}$) higher than that of 2-butanol ($\ce {99 ^\circ C}$)?
The only reason I can think of is ...
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How to calculate which ionic compound has the highest melting point?
Which of the following compounds has the highest melting point: $\ce{PCl5}$, $\ce{H2O}$, $\ce{NaCl}$, $\ce{SrCl2}$, $\ce{CaF2}$?
In general, ionic compounds will have higher boiling points than those ...
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Why ethyl cyanide and propanol have the same boiling point?
As I understand, the intermolecular forces of ethyl cyanide are of van der Waals nature (dipole-dipole) but in the propanol molecule there are hydrogen bonds which are in principle much stronger. Why ...
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Can we predict the IMF strength of Acetone vs Glycerol?
I was recently assigned a lab where I was to observe several properties of the chemicals Acetone and Glycerol then use my observations to predict their overall Intermolecular Force strength.
The ...
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Why is polymer B more dense than polymer A?
The official solution is that A has branched / side chains, weak Van der Waals forces between the polymer chains, less compact packing than B, and large inter-chain distances.
B has no branched chains,...
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Forcing atoms closer together [closed]
Is there a method in chemistry to alter the energy of atomic bonds by forcing atoms closer together in a smaller volume?
Similar to how pressure squeezes atoms closer together.
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Why does diethylmethylamine have such a low melting point?
According to PubChem, diethylmethylamine has a remarkably low melting point of $-196.0\ \mathrm{^\circ C}$. This is substantially lower than the melting points of dimethylethylamine ($-140.0\ \mathrm{^...
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Without attractive forces, why would there be only ideal gases? [closed]
I've read this statement in several places. What is the importance of attractive forces for solids and liquids?
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Relative strength of intermolecular forces [duplicate]
My attempt at a solution:
First I look for hydrogen bonds:
The only compounds with hydrogen bonds are the second and fourth ones, so they have the strongest intermolecular forces. The second must have ...
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Anomalous boiling point of "iso-" alkanes
I was attempting to compare the boiling points of iso-hexane and 3-methylpentane.
Boiling points of organic compounds depend upon three factors according to Master Organic Chemistry – 3 Trends That ...
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Do amines or alcohols have stronger intermolecular hydrogen bonds?
Which has stronger hydrogen bonding, $\ce{CH3OH}$ or $\ce{CH3NH2}$
I think it comes down to which has more dominance; number of hydrogens, number of lone pairs, or electronegativity.
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What repulsion keeps non-hydrogen atoms at a distance: between inner shells or between nuclei?
Bonded or not, when two atoms or ions come closer than the bond distance or the van der Waals distance, the energy increases drastically. What is the underlying cause of that repulsion?
The repulsion ...
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Melting and boiling points of benzene and fluorobenzene
This species is a derivative of benzene, with a single fluorine atom
attached. Its melting point is -44 °C, which is lower than that of
benzene, indicative of the remarkable effect of fluorination ...
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Why are fluoroalkyl chains hydrophobic/oleophobic?
I'm searching for an answer that explains the hydrophobicity / oleophobicity in terms of intermolecular forces, but can't really find one.
Below is an example fluoro-alkyl nano-particle, F-POSS. It ...
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Why is carbon tetrachloride a liquid at room temperature? [duplicate]
From what I can understand, $\ce{CCl4}$ has only London dispersion forces between its molecules. However, it is still liquid at room temperature. $\ce{CCl4}$ has just five atoms, making it a ...
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Why do chloroform and benzene exhibit negative deviation from Raoult's law?
Chloroform is a polar molecule, and benzene is nonpolar. Shouldn't the chloroform-chloroform and benzene-benzene intermolecular forces be stronger than chloroform-benzene interactions (like dissolves ...
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Reasons for solid or liquid soap
Soap is made by a saponification reaction, where a fat reacts with hydroxide ions to form a surfactant and glycerol.
To make a solid soap $\ce{NaOH}$ is used, while $\ce{KOH}$ is used for liquid ...
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work and chemical bonds [closed]
If breaking bonds is endothermic (takes energy), and work is force over a distance-
Would breaking bonds require "work"? Or do we only need heat energy? I'm trying to understand how to ...
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Casimir effect and van der Waals forces
The Casimir effect makes two close metal plates in a vacuum attract.
I was pondering and figured out that two close molecules should experience the same effect, as they are close and between molecules ...
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Why is boiling point of carbon tetrachloride greater than silicon tetrachloride?
$\ce{CCl4}$ and $\ce{SiCl4}$ both are non polar molecules thus London forces must be the only forces of interaction.
Then London forces are supposed to be greater in $\ce{SiCl4}$ due to its larger ...
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Critical separation at which molecule breaks
I have the following question.
The potential energy of two atoms, a distance $r$ apart, is: $$U = -Ar^{-2} + Br^{-10}$$ Given that the atoms form a stable molecule at a separation of $\pu{0.3 nm}$ ...
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Atoms and their vibration [closed]
We all know that the atoms in any solid matter vibrate about their mean position but why do they do so?? What will happen if they stop vibrating??
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Ozone in ozone layer [closed]
If ozone is a gas, and gases have the highest entropy, then how does the ozone gas stay within a few layers of the atmosphere, even though they span for kilometers?
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Pressure of a system of particles
I'll derive the pressure of a system of particles, which would be used in a MD simulation for example, according to Allen's Computer Simulation of Liquids and show where my issue is.
Consider a ...
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it is possible for the hydrogen bond to form between the hydrogen chloride molecule, HCl? [duplicate]
Recently I'm doing my work, and I can't find what it is the answer. Can you guys help me?
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When non-polar particles interact through dispersion forces, how fast does a temporary dipole induce a dipole in the neighboring molecule?
The current question is inspired by this existing question: At what frequency does a non-polar molecule acquire a dipole able to participate in London Dispersion forces?. In the comments and answers, ...
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What are the cheapest basis sets able to model intermolecular dipole interactions inside a metal complex and give good relative energies, with DFT?
As a example, If I have a square planar complex of a cation with both a weakly polar ligand (X) and strongly polar ones, like ammonia and water I expect a bit of stabilization due to formation of a ...
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Why are Buckminsterfullerene (C60) solutions pink/purple?
A solution of Buckminsterfullerene $\ce{(C60)}$ is shown below:
According to the April 8th Wikipedia page on Buckminsterfullerene $\ce{(C60)}$:
Solutions of pure C60 have a deep purple color which ...
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Why is the boiling point of ethyl fluoride lower than that of hydrogen fluoride?
The book, Solomons' Organic Chemistry (for JEE Mains and Advance), contains the following question:
Hydrogen fluoride has a dipole moment of $\pu{1.82 D}$; its boiling point is $\pu{19.34 ^{\circ} ...
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Boiling points of ethylene, formaldehyde and oxygen
The boiling points of ethylene, formaldehyde and dioxygen are $\pu{-103.7 ^\circ C}$, $\pu{-19 ^\circ C}$, and $\pu{−183 ^\circ C}$, respectively. I expect formaldehyde to have the highest boiling ...
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Intermolecular Forces of Attraction [closed]
Imagine a bottle 85% filled with water and the rest is just air, and the cap is closed. Here are now my questions.
Since the cap is closed completely, the air bubble is formed. Is that air bubble ...
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How does molecular structure affect physical properties?
The question sounds vague and non-specific because my background in chemistry is limited to undergrad college courses. However, I am interested in learning the correlations between the atom-by-atom ...
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Solubility of alcohols in non-polar solvents
The solubility of an alcohol in a non-polar solvent (like hexane) increases with size of the alcohol, as the non-polar chain increases. However, as the chain keeps increasing, will the solubility ...
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How big does an atom need to be to have dispersion forces be greater than other intermolecular forces? [closed]
I know as an atom gets bigger the dispersion forces grow with it. But how big does an atom, e.g methanoic acid, to have dispersion forces that outrank dipole-dipole forces?
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Is Tkatchenko's MBD-NL method self-consistent?
I have a question regarding Tkatchenko's [1] new nonlocal many-body dispersion method (MBD-NL). Does anyone know if it's a self-consistent method? I read this paper many times but I'm still not sure.
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How does sugammadex (a modified cyclodextrin) draw rocuronium into its lipophilic cavity?
Sugammadex is a modified cyclodextrin: 8 member sugar ring with carboxyl thioether extensions. Rocuronium is an aminosteroid, 4 steroid rings and one protonated amine group.
Sugammadex binds ...
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