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 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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Is a temperature decrease required for hydrogen bonds to form in water?
As I understand it, increasing the temperature of water causes hydrogen bonds to break. Does this mean that a decrease in temperature is required for the formation of those hydrogen bonds?
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Does ozone has dipole forces [duplicate]
Considering ozone in liquid state, certainly there are london forces, but does the position of its molecules induce dipole intermolecular forces?
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What is a hydrogen bond acceptor and donor?
I recently read about hydrogen bonding. One thing about which I am really confused is how to distinguish between hydrogen bond acceptors and donors.
I looked it up on SE and found this post, which ...
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What is the underlying chemistry behind the triboelectric effect?
I remember briefly studying the triboelectric effect in Physics but as I now approach the domain of Chemistry, I'd like to know what processes are involved (at the molecular level) when the the ...
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How to calculate Lennard-Jones potential with quantum mechanical methods
I want to know the procedure to calculate the Lennard-Jones potential for a metal-halogen pair (specifically vanadium-chlorine). Is it possible to calculate using any QM packages like Mopac, NWChem, ...
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Intermolecular forces between C and Na2O [closed]
I was trying to do an experiment called Pharaoh's Serpent and I read that the intermolecular forces between the $\ce{C}$ and the $\ce{Na2O}$ (formed in the thermal decomposition of the $\ce{NaHCO3}$) ...
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Why a particular enantiomer of a diastereomer shows affinity towards another? [closed]
A particular enantiomer can show affinity towards another enantiomer of another diasteromer eg. body receptors with chiral drugs, chiral stationary phase of chromatography etc.
But what's the reason ...
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Why do lone pairs of electrons have a higher repulsive force? [duplicate]
I was just wondering why lone pairs of electrons are more repulsive than bonded pairs of electrons.
I have read that lone pairs have orbitals which are shorter and more round, compared to bonded ...
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Strength of Dipoles, Covalent bonds and H-Bonds
My textbook says:
Dipole-dipole forces are 1% as effective as covalent bonds and the strength of a hydrogen bond is generally twenty times less than that of a covalent bond.
What do these ...
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Why do alkenes with more surface contact have greater London forces?
Why is it that alkenes with greater surface contact have greater London forces? I thought greater London forces were dependent on the size of the molecules, or the number of electrons, rather than the ...
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Why does branching decrease density and melting point?
The general explanation given is that the chains are further apart, so the intermolecular forces are less, and as they are further apart, they occupy more volume, and the density is lesser. But the ...
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AP Chemistry Practice exam [closed]
It's starts off the question with "Propanoic Acid, $\ce{C2H5COOH}$, is an organic acid that is a liquid at room temperature. An incomplete Lewis diagram for the propanoic acid molecule is provided in ...
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Mixing water and oil in microgravity outside of a container
What would happen if I where to mix water and oil in a vacuum in microgravity where the temperatures were low enough so that the oil and water remain liquids also, the mixture is not inside of a ...
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Which of these functional groups is soluble in aqueous HCl and/or NaOH?
http://pastpapers.papacambridge.com/view.php?id=Cambridge%20International%20Examinations%20%28CIE%29/AS%20and%20A%20Level/Chemistry%20%289701%29/2015%20Jun/9701_s15_qp_42.pdf
I need some help to ...
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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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How does cross-linking between polymer chains increase the melting point of the polymer?
https://i.sstatic.net/uUcQr.jpg
Suppose we have this polymer chain. Now, we cross link some chains ( not all ) , so some chains get linked, and others remain as they are. What we now have is a '...
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How to determine relative polarity (basic procedure)? [closed]
I am taking AP Chemistry, and have noticed that I can identify a polyatomic polar molecule, but struggle to determine which molecule is the most polar given a set of several polar molecules.
What ...
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Dielectric constant and dissolution of ionic salts
We say that salts like $\ce{NaCl}$ get easily dissolved in water because the dielectric constant of water is very high. I know the dielectric constant of water is 81 and if a salt is put into water ...
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Non-polar molecules are soluble in non-polar solvents (hexane) but not in water, Why?
My book says that non-polar simple molecular substances can dissove when added to a non-polar solvent, such as hexane due to intermolecular forces forming between the molecules and the solvent.
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How well can triglycerides be resolved using TLC?
The only part of triglycerides that significantly interacts with a TLC plate are the ester moieties which are present in all triglycerides. Other than that, they do not differ much, except in mass (...
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When is a dipole-dipole interaction strongest?
Are there any conditions that'll improve the interaction? Just like, I assume, hydrogen bonds are strongest when the difference in electronegativity is biggest.
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Do dipole dipole interactions need to be added explicitly to vdW forces while doing DFT simulations for organic molecules?
I am modelling the adsorption of organic molecules on metal surfaces using plane-wave dft. While there is literature on how important van der Waals forces are for organic systems, and there are also ...
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Which is more soluble in water, HF or SO2?
I was wondering which is more soluble in water, hydrogen fluoride or sulfur dioxide? Since $\ce{HF}$ will hydrogen bond to other HF particles (as opposed to $\ce{SO2}$ dipole-dipole attraction).
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Why is the pressure correction in the van der Waals equation proportional to (n/V)^2?
The van der Waals equation for real gases is stated as follows:
$$\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$$
For the coefficient $b$, we can reason out that more the number of molecules, the ...
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If polar non-polar intermolecular forces are stronger, why do polar compounds elute first in GC?
I remembering reading that the interaction between a polar molecule and non-polar molecule is stronger than the interaction between two non-polar molecules.
However, in analytical chemistry classes, ...
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High Degrees of Symmetry in Molecules
I recently encountered a question on a test:
Substances whose molecules have a high degree of symmetry will have:
A. a low specific heat
B. a high melting point
C. a high heat of ...
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Interaction between a pencil and rubber (eraser)
Is there a interaction between a graphite pencil and and a eraser. For example, if I drew a line on a piece of paper and then erased that, what interaction is occurring?
Is it a Van der Waals ...
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Lennard-jones cut-off
I am using a Lennard-Jones potential in a computer simulation and I was wondering if i should place a cut-off for low distances since the potential blows up quickly making the calculations quite ...
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London/dispersion forces
"London (dispersion) forces are responsible for the fact that non-polar substances can be condensed to form liquids and sometimes solids at low temperatures"._
I learned that what results in London ...
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Difference between Force Field and topology, and other related questions
I am performing some Molecular Dynamics computer simulations and I am learning about the various Force Fields (FF) such as OPLS-AA, OPLS-UA, AMBER, etc.
Many things are still unclear to me. I put ...
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Force Fields and units
I am a math student trying to implement a simple force field in python for determining the energy of a small molecule and trying to minimize it in order to find a stable configuration. I was wondering ...
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Intermolecular forces between carbon dioxide and water
I'm wondering which intermolecular forces will exist between carbon dioxide and water. Instinctively, I would expect there to be only dispersion forces between the 2 molecules, because carbon dioxide ...
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How DFT-D3 incorporates coordination number (CN) into C6
I'm reading Grimme's DFT-D3 paper
but really puzzled by how the $\mathrm{CN}$ is considered in the calculation of $C_\mathrm{6}$ coefficients. (Stefan Grimme, Jens Antony, Stephan Ehrlich, and Helge ...
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Dipole-quadrupole polarizability term for induced dipole
For describing an induced dipole, I have usually seen the following equation,
$$
P_{i} = \alpha_{ij}E_{j} + \frac{1}{2}\beta_{ijk}E_{j}E_{k}
$$
where $P_{i}$ is the $i^{\text{th}}$ component of the ...
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Why is the polar-nonpolar electronegativity difference defined to be 0.4?
In introductory college chemistry, bonds between elements that have an electronegativity difference $\Delta EN > 0.4$ are generally consider to be polar (and thus have a dipole moment), while $\...
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Recommendations for electrostatic potential surfaces
Are there standards for density cutoffs, colours and colour mappings for electrostatic potential surfaces?
I observe that people use many different values.
For instance, this article (in Fig. 1a) ...
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Why is Trouton's rule not valid for liquids with boiling points less than 150 K?
This is a question from the last year's semester examination.
Why is Trouton's rule not valid for liquids with boiling points less
than 150 K?
I searched the internet but only found that the ...
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Does oxygen gas form hydrogen bonds?
I learned that hydrogen bonding is formed from a 'sandwich' of hydrogen and either oxygen, nitrogen, or fluorine where nitrogen, fluorine, or oxygen is the bread.
Will oxygen gas and water form ...
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Which potentials are suitable for molecular dynamics simulation of simple explicit solvents?
Which potentials (force fields) are suitable for adequately simulating (mixtures of) explicit solvents? Interesting rheological properties include viscosity, surface tension, heat capacity.
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Computational Chemistry: calculation of sterical effects
Is there a way to calculate sterical forces between atoms/groups of atoms (preferably with free and open source tools)? I have heard that this is possible within the framework of NBO. I am using ORCA, ...
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What is the exchange interaction?
As the wikipedia article for the exchange interaction so aptly notes, exchange "has no classical analogue."
How wonderful.
Exchange shows up essentially while enforcing the condition that two ...
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Is it possible to have a dispersion interaction with no inductive interactions?
In symmetry-adapted perturbation theory, the interaction energy of a non-covalently bound pair of molecules (it could be done to arbitrary order but is usually just pairs) is built up from a ...
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Work to overcome adhesion of a liquid to a solid
I'm interested in the van Der Waals force of a liquid adhered to a solid. For example, if you spray some water on a vertical piece of glass, the little droplets with adhere to the window rather than ...
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Fitting of interatomic potentials to a training set
I have read several times in the literature the following:
"The fittings were accomplished using a combination of the singular value decomposition method for linear parameters and the Simplex method ...
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What is the potential to use for non-dispersion interactions?
Although liquid argon’s intermolecular potential can be described using a Lennard-Jones (LJ) potential, which takes into account dispersion forces (induced dipole-induced dipole interactions), what ...
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Why is the boiling point of water and ammonia so different?
Boiling point of water is 100 degrees Celsius, while boiling point of ammonia is minus 33 degrees Celsius, which makes 133 degrees difference. Now when we discuss value of boiling point, we also say ...
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How to illustrate London forces?
This may be too subjective for this forum, but I'll take my chances.
For the purposes of a "quick and dirty" illustration of London forces, I'm looking for best practices and creative ideas. For ...
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Most likely intermolecular force in aqueous ethanol
The most likely interaction to be found in an aqueous solution of ethanol is
A. London dispersion forces
B. Hydrogen bonding
C. Dipole-dipole interactions
D. Ion-dipole interactions
I am split ...
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Why is the melting point of KBr higher than that of CsCl?
I thought that when compounds have similar forces and charges, the one with the higher molecular weight has the higher melting point. If that is true, then why is the melting point of $\ce{KBr}$ ...
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