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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1answer
4k views

How do you calculate the dipole moment of larger molecules?

I know that the dipole moment is obtained by: $$ \vec{\mu} = Q \cdot \vec{d} $$ with the condition that charges of a pair of atoms are equal and opposite, i.e. $\ce{NaCl}$. But, in order to obtain ...
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2answers
62 views

Why does dipole must lie parallel to a rotation symmetry axis?

While studying group theory, I've got confused by the following statement: For a molecule to have a permanent dipole moment, it must have an asymmetric charge distribution. The point group of the ...
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0answers
38 views

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? ...
3
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2answers
223 views

Link between centrosymmetry, dipole moment and chirality

What is the relationship between the three concepts in the title? I know all centrosymmetric molecules are achiral, but not all achiral molecules are centrosymmetric. Thus, there are no molecules ...
19
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2answers
40k views

How does a lone pair of a central atom affect the dipole moment?

Dipole moment is the degree of polarity, i.e. the seperation of positive and negative charges. But I am not getting the intuition why and how lone pairs affect the polarity and dipole moment. I cannot ...
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50 views

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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0answers
39 views

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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191 views

Why does the dipole moment order of group 15 hydrides increase down the group?

The order given in my book is $$\ce{NH3} > \ce{SbH3} > \ce{AsH3} > \ce{PH3}$$ Phosphorous is more electronegative than arsenic and antimony. Then shouldn't the dipole moment be more in ...
22
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3answers
8k views

Dipole moments of pyrrole and furan

Why do pyrrole and furan have dipoles oriented in different directions?
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2answers
5k views

Non-zero dipole moment of hydroquinone

Why does hydroquinone possess a non-zero dipole moment? The $\ce{OH}$ groups present at para positions on the benzene ring should cancel the effect of each other... if there is a plane change then ...
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2answers
29k views

Why is water a dipole?

Water ($\ce{H2O}$) is a dipole. The reason why is simply because it is not symmetrical, there are more electrons on the oxygen side than on the hydrogen side, and the electronegativity of oxygen. But ...
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29 views

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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2answers
172 views

Dipole moment of water using the definition [closed]

In many Chemistry books, the dipole moment of molecules is calculated through algebraic formulas. However, another definition of the dipole moment is $$\vec{\mu} = \sum_i q_i \, \vec{r}_i$$ So, how ...
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163 views

Comparing dipole moments of Ortho,para and meta compounds

I was doing some questions based on dipole moment ortho,met and para compounds. I was not able to understand why dipole moment for \ce{C6H4NH2NO2} increases from ortho to para Because i think \ce{NH2} ...
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2answers
2k views

Dipole moment of symmetrical molecules

While studying dipole moment in organic chemistry, I got stuck at a particular statement written in the book : Symmetrical molecules without lone pairs of electrons will have $\mu = 0.$ The main ...
6
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0answers
208 views

Why is the dipole moment of XeF$_6$ zero? [duplicate]

In Concise Inorganic Chemistry by JD Lee (4th edition; adapted by Sudarshan Guha), page 73 under the section 3.6 (VSEPR Theory chapter Chemical Bonding): ...according to this theory, the position ...
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46 views

Finding Bond moment of O-H bonds of water

While finding bond moment of water we take the dipole moment of water as the vector sum of two O-H bonds and we calculate it to be 1.51D. But the lone pair is also present which affects the dipole ...
2
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1answer
85 views

Why does dielectric constant of crystal fluctuates in case of Frenkel defect in a crystal?

So I was studying Frenkel defect in crystal and came across this line that said The closeness of like charges tends to increase the dielectric constant of the crystal. I'm not able to understand ...
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2answers
624 views

Why is the dipole moment of acetone higher than ethanol?

It is true that acetone is less polar than ethanol. I thought the dipole moment is proportional to polarity, and if so, the dipole moment of acetone should be lower than ethanol. But the dipole ...
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0answers
46 views

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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3answers
9k views

Why is the dipole moment of ethyl chloride larger than that of vinyl chloride?

The dipole moment of ethyl chloride is 2.10 D (J. Mol. Struct. 1990, 216, 9–26), and that of vinyl chloride is 1.42 D (J. Chem. Phys. 1960, 32 (1), 205–209). Why is this the case? I would have ...
14
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1answer
5k views

Order of dipole moments

What is the order of dipole moments for $\ce{SO3, SiO2, P2O5,}$ and $\ce{Cl2O7}$? This question is from a book and the answer given is $\ce{Cl2O7 < SO3 < P2O5 < SiO2}$. Can someone explain ...
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2answers
30k views

Why is HCl not considered to have hydrogen bonding?

A molecule that has hydrogen bonding usually follows these two premises. 1.) There is a hydrogen atom involved 2.) Hydrogen must be bonded to a highly electronegative element which are ...
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1answer
30 views

What is the meaning of moment in Dipole moment [duplicate]

Today I read about dipole moment in my standard textbook. It said something like it is the measure of charge separation, and then proceeded to the formula , ie. Delta'charge'×bond length. But I can't ...
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1answer
82 views

Why must polar molecules be asymetrical? [duplicate]

As I understand, polarity in molecules comes from the difference in electronegativity or the ability of the atoms to attract eletrons so the electrons spend more time or are more probable to gravitate ...
4
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1answer
114 views

Qualitative Comparisons of Dielectric Constants of Organic Solvents

This question is inspired by the discussion around this earlier question. It is relatively simple to do a qualitative comparison of the polarities of different molecules (for example by analyzing the ...
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1answer
2k views

Why Benzene is a good solvent even while it is not polar

Consider for a moment, ether, THF, benzene and hexane. Why is the solubility of many organics in these solvents in the following order THF > ether / benzene > hexane What makes benzene a good ...
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1answer
69 views

dipole–dipole interactions: OCR Sample Paper wrong? [closed]

I was doing OCR A Level Chemistry A, H432/01 Periodic table, elements and physical Sample Question Paper. Question 6 was: The boiling point of hydrogen bromide is –67 ºC. The boiling point of ...
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1answer
537 views

Why are the dispersion forces in CS2 stronger than the dipole-dipole forces in COS?

London dispersion forces supposedly have the least strength out of all the intermolecular forces. But $\ce{CS2}$, which has only dispersion forces, has a higher boiling point (and thus stronger ...
3
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1answer
806 views

Calculating the ionic polarizability from the Clausius-Mossoti relation

The concentration of atoms in a crystal is $N_d = \pu{2.24e28 m-3}$, and the relative dielectric constant is $\varepsilon_{r} = 5.62$. The crystal has a refractive index of $n = 1.5$. Using the ...
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33 views

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 ...
2
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1answer
247 views

Which has a greater dipole: chloroform (CHCl3) or trichlorofluoromethane (CCl3F)?

Does chloroform have a greater dipole because the $\ce{C-H}$ dipole is weaker than $\ce{C-Cl}$ dipole thereby making the overall net dipole greater in chloroform, as opposed to trichlorofluoromethane ...
28
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2answers
11k views

Confusion about direction of dipole arrow in alpha-helices and other molecules

I understand that molecular dipoles are electric dipoles. And electric dipole moment vectors point from the negative to the positive charge. In class we learned to draw these special molecular dipole ...
7
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1answer
547 views

Why does acetonitrile have a larger dipole moment and boiling point than acetaldehyde?

Experimentally, acetonitrile has a larger dipole moment than acetaldehyde, but I've never understood why. I always thought that the charge separation between carbon/oxygen is larger than that of ...
12
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2answers
1k views

How to identify hydrogen bonds and other non-covalent interactions from structure considerations?

Chemistry is governed by a wide range of interactions, from ionic and covalent bonding, or other types of strong interactions, towards weaker types of bonding, attraction, or repulsion, that typically ...
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1answer
230 views

Why does phosphine have a dipole moment and a higher boiling point than carbon tetrafluoride?

Phosphine, PH3, and carbon tetrafluoride, CF4, are small molecules of a similar size and the same mass of 88 au. CF4 has a dipole moment of 0, which is unsurprising given its tetrahedral shape. ...
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2answers
243 views

Which Oxygen atom in HCOOH (formic/methanoic acid) does Carbon donate its electrons to, to obtain a partial positive charge?

I was wondering if the Carbon atom in HCOOH (methanoic/formic acid) forms a positive partial charge by donating its electrons to both the Oxygen atoms, since they both possess a higher ...
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0answers
472 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 ...
9
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2answers
197 views

Why is ammonia still considered polar despite undergoing rapid inversion?

Here it is stated that a molecule with a rotation axis cannot have dipole moment perpendicular to the axis, as any dipole moment would be changed upon rotation about this axis (which preserves the ...
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1answer
83 views

how can a covalent molecule with a permanent dipole still have temporary dipoles?

As I have read online, temporary dipoles occur due to the random fluctuations of the electron cloud. The electrons move randomly to one side of the molecule creating a negative partial charge while ...
7
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1answer
71k views

Dipole moment - calculation of percentage ionic character

Question: The dipole moment of $\ce{HBr}$ is $2.60 \times 10^{-30}$ and the interatomic spacing is $1.41$. What is the percentage ionic character of $\ce{HBr}$? What I know is that the percentage ...
0
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1answer
105 views

What are the intermolecular forces between polychloroethylene?

Does polychloroethylene have only van der Waals/London forces between its molecules? Surely, if all the chlorine atoms are on one side, due to the fact that chlorine is more electronegative than ...
2
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1answer
3k views

How to determine what organic molecule has the highest boiling point?

Compare and answer which one has the highest boiling point: $\ce{CH3CH2CH2CH3}$ (butane) ... [$\pu{−1}$ to $\pu{1^\circ C};\ 30$ to $\pu{34^\circ F};\ 272$ to $274\ \pu K$] $\ce{CH3NH2}$ (...
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1answer
5k views

Relationship between dipole moment of a molecule and electronegativities of constituent atoms

I want to know if I can calculate the dipole moment of a molecule given the electronegativity values for the atoms comprising it. I think that dipole moments determine the polarity of molecules, so ...
10
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2answers
52k views

Is carbon dioxide IR inactive?

I am told that carbon dioxide is IR inactive. This somehow strikes me as untrue or at best oversimplified, because yes, it is overall symmetrical, but can't $\ce{CO2}$ be induced to show asymmetric ...
2
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2answers
415 views

How does one apply the knowledge of the direction of a molecular dipole moment?

I was watching Khan academy's video about molecular dipole moments, which explained what they are and how they can be calculated. I also read this article. Both sources explain the concept similar ...
7
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4answers
32k views

Why is tetrafluoromethane non-polar and fluoroform polar?

Consider the Lewis dot structures of the molecules fluoroform, $\ce{CHF3}$, and tetrafluoromethane, $\ce{CF4}$:   My first line of thought is that both of these molecules are symmetrical (the ...
2
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2answers
56 views

Directional emission from molecules

This might be a silly question (probably is). When a molecule absorbs it has a transition dipole moment, a measure of how strongly a certain transition will interact with light will depend on how ...
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2answers
1k views

Hydrogen bonds - why not in HCl? [duplicate]

In a textbook1, I found the following clear definition of hydrogen bonds: The strongest secondary bonding type, the hydrogen bond, is a special case of polar molecule bonding. It occurs between ...