Questions tagged [dipole]

For questions about the dipole moment of a bond or a molecule; its calculation, comparison with other bonds or molecules, affect on molecular properties, etc.

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How to calculate transition dipole moment from two known wavefunctions

I am interested in calculating the transition dipole moment (TDM) from the information from two wavefunctions of different states. This is somewhat similar to calculating the molecular dipole moment ...
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Why does 1,4-diiodobenzene have a non-zero dipole moment?

From this answer, I came to know that 1,4-diiodobenzene has a dipole moment of $0.19~\rm D$ in benzene at $20\ ^\circ\rm C$. On the basis of symmetry, I'd expect the bond moments due to the difference ...
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Program to compute multipoles of water at CCSD(T)-F12 accuracy

I want to compute traceless cartesian electrostatic multipole moment tensors up to fourth order (hexadecapole), at CCSD(T)-F12 accuracy using a large basis set. I'd like to be able to choose the ...
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5 votes
1 answer
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How to explain the periodic trends in boiling points in groups?

Observing the trend of boiling points of the compounds listed, choose the appropriate terms to fit into the blanks: \begin{array}{lr} \hline \text{Compound} & \text{b.p.}/\pu{°C}\\ \hline \ce{H2Te}...
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4 votes
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Why do molecules showing a pure rotational spectra require a permanent dipole?

I understand that pure rotational spectra only exist for molecules which have a permanent dipole moment. The common explanation is "so that they can interact with the E-field of the incoming ...
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Can we find dipole moment of water from a familiar property?

There are many videos on Youtube showing deflection of a stream of water by a charged rod. My question is whether we can do a rough calculation of the dipole moment of water molecules using this ...
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Why is there only little difference between molecular dipole moments in CHX3 compounds (X = Cl, Br, I)?

Why is there only little difference between molecular dipole moments in $\ce{CHX3}$ compounds ($\ce{X}$ = $\ce{Cl}$, $\ce{Br}$, $\ce{I}$)? As we can see there is a huge difference in dipole moment of ...
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Why is the intensity of the IR spectra of IBr higher than that of ICl?

Why is the intensity of the IR spectra of $\ce{IBr}$ higher than that of $\ce{ICl}$? I know that the IR spectra intensities are proportional to the derivative of the dipole moment with internuclear ...
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Do I understand correctly that simulation volume influences relative permittivity calculations? If so, how is the result useful?

I am having a lot of trouble understanding the influence of volume on relative permittivity/static dielectric constant. I'm not a chemist, but am using molecular dynamics to calculate relative ...
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Perturbation theory for molecules, chromophore group, dipole approximation,

I am interesting in chromophore group and dipole approximation. For example, i have a molecule (acetone or any other ketone/enol) which is belongs to some symmetry group. Because of the symmetry ...
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For a given period, why is the boiling point of the halogen greater than that of the noble gas?

The boiling point of bromine, a halogen, is $\pu{58.8^\circ C}$, while the boiling point of krypton, the noble gas in the same period as bromine, is $\pu{-153.4 ^\circ C}$. I thought that the larger ...
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What is the need for dipole moment if electronegativity already exists?

Say we have an HCl molecule. The difference in electronegativities of the H and Cl atoms tells us how polar the HCl molecule is. The dipole moment is also a measure of the degree of polarity in ...
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Lone pair and dipole moment of ozone

(This is a question similar to this and this, but none of the answers to those two questions answer my question.) I've seen many places explain the dipole moment of ozone from the formal charges of ...
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Which has more ionic character, LiF or K2O?

After drawing the structures of both and considering dipole moment, doesn't it seems that all K2O should have more ionic character than LiF? My textbook says its LiF.
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How does hot air remove guests from cyclodextrin?

Cyclodextrin, as I know, has a hydrophobic cavity. Therefore, it would absorb hydrophobic organic compounds. But the organic compound can also be removed with hot air since the interaction between the ...
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2 votes
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579 views

Boiling point and Intermolecular forces

After looking for proper reasons for boiling point orders, nobody could even explain why $\ce{CCl4}$ has a higher boiling point than $\ce{SiCl4}$, but after looking for patterns, in lots and cases of $...
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Dielectric polarization: how to identify what part of the total polarization (dipolar+electronic+ionic) I need (conceptual question, I use DFPT, VASP)

I am doing polarization calculations to get data for use in other calculations. To start with, I want to calculate the static dielectric constant. However, I'm a newbie to polarization and it is a ...
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When do lone pairs affect dipole moments?

My textbook says that NH3 has more dipole moment than NF3 despite F being more electronegative than H, because the dipole moment due to the lone pair on N points in the same direction as the ones due ...
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Factors dominating forces between acetone and chloroform

What type of interaction is present between acetone and chloroform? According to me, acetone has weak hydrogen-bonds with chloroform, the hydrogen on an electronegative atom has electron density that ...
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103 views

Effect of ionization on dipole moment

Suppose we have a non-dipolar molecule such as carbon dioxide. If carbon dioxide is ionized by some means in the gas-phase, will it develop a dipole moment? I am asking with reference to microwave ...
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Why London force dominates in Alkyl Halides

Why London Force is greater than dipole-dipole interactions in Alkyl Halides? As we know that most of the time London force is weaker than other forces. Then why in this case it's not so? ...
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Dipole moments of dibromoethene isomers

There was an exercise in my textbook asking to compare the dipole moments of 1,1-dibromoethene and 1,2-dibromoethene(Z). The answer in the textbook says that the dipole moment of 1,1-dibromoethene is ...
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1 vote
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1k views

Dipole moment in aromatic compounds

Compare the dipole moment of the following: o-nitrophenol o-dichlorobenzene o-xylene What I thought was: o-dichlorobenzene should have the maximum, due to the acute angle and being more ...
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1 vote
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120 views

Closed shell structure & intrinsic molecular (electric) dipole moment

Does the closed shell structure of a molecule imply that it has an intrinsic (electric) molecular dipole moment? If so, why is that? I came across this in paper [1], which seems to suggest that this ...
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How is it possible to get an attractive charge-dipole interaction using the modified Coulomb law?

Vqµ = − qµ / (4π ε0εr r2) Say you had a negative charge, interacting with the positive end of a dipole then the charge would be -1.602 x 10-19 C and the dipole moment would always be a positive value....
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Is the momentary dipole in between a cell membrane due to the van-der-Waals forces?

There are van-der-Waals forces within non-polar molecules. I read it that is mainly due to the instantaneous movements of the electron cloud's distribution. When looking at symmetrical molecules like $...
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Comparing dipole moments of hydrogen halides

How can we compare dipole moments of halide ions? As we go down the group, the induced charged hydrogen decreases as electronegativity difference between hydrogen and corresponding halogen decreases ...
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How to convert from dipole derivative to atomic units?

I need to convert dipole derivative output by Gaussian into atomic units. The dipole derivative is given in Gaussian in the weird units $(\mathrm{km/mol})^{1/2}$. I know that $\pu{1 D^2/(Å^2amu)}$ = $\...
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47 views

Are spontaneous/induced dipoles the same as van der Waals forces?

I am puzzled by the names of dipoles. What is the difference among permanent dipoles, spontaneous dipoles, van der Waals forces, and intermolecular forces? Does "The intermolecular force" ...
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TD-DFT transition dipole moment vector does not align with experimental data

I have been modelling excited states of some molecules with similar stucture using TD-DFT theory, however, I have encountered an issue that sometimes transition dipole moment does not align with the ...
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What is the link between the classical and quantum definition of the symmetry number?

From what I understand, the symmetry number for a molecule can be defined in 2 ways: 1. The quantum mechanical symmetry number corrects for overcounting the number of possible rotational states of a ...
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Deriving the absorption coefficient from state transitions

This source states that the absorption coefficient $\gamma$ is proportional to the difference in particle number density $\Delta n$ per unit volume between the initial and the final rotational state ...
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Theoretically predict the density of water

Is it possible to predict the density of water having just its molecular structure (basically obtain 1 g/cm3 at 3.96 °C)? Are you aware of research/textbook that dive into this topic? Is it able to ...
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301 views

Why don't I get the same value of percentage ionic character of a particular molecule from different equations?

About the ionic character of a polar covalent compound Pauling gave two equations as [1-$e^{.25(x_a - x_b)}] $% [18$(x_a-x_b)^{1.4}$]% Hanary and Smith gave the equation [$16(x_a-x_b)+3.5(x_a-...
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2k views

Deciding if a molecule is polar and non-polar in cyclic carbon compounds

While discussing about dipole moment of the compounds, our chemistry teacher told that the dipole moment will be 0 for 1,4-Dichlorobenzen, and for those compounds where same atoms or group of atoms ...
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136 views

Why is the molecular dipole the main determinant of whether a substance dissolves in another substance?

Consider a covalent molecule such as carbon tetrafluoride. In $\ce{CF4}$, each $\ce{C-F}$ bond is polar covalent. However, this substance is considered overall non-polar because each bond dipole ...
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-1 votes
1 answer
88 views

How does this rotation minimize the dipole moment?

A paper I'm reading says: The low energy conformation of 3 minimizes the overall dipole moment of the compound and thus rotates the exocyclic amide 180° from desired conformation, as can been seen in ...
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