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.
147
questions
15
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0answers
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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 ...
6
votes
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 ...
2
votes
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 ...
1
vote
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
votes
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
votes
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 ...
0
votes
0answers
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 ...
2
votes
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 ...
1
vote
0answers
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
votes
3answers
8k views
Dipole moments of pyrrole and furan
Why do pyrrole and furan have dipoles oriented in different directions?
19
votes
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 ...
25
votes
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 ...
1
vote
0answers
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 ...
1
vote
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 ...
0
votes
0answers
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} ...
2
votes
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
votes
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 ...
0
votes
0answers
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
votes
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 ...
0
votes
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 ...
3
votes
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 ...
6
votes
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
votes
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 ...
10
votes
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 ...
-1
votes
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 ...
0
votes
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
votes
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 ...
4
votes
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 ...
1
vote
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 ...
6
votes
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
votes
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 ...
2
votes
0answers
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
votes
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
votes
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
votes
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
votes
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 ...
0
votes
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. ...
1
vote
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 ...
1
vote
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
votes
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 ...
-1
votes
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
votes
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
votes
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
votes
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 $274\ \pu K$]
$\ce{CH3NH2}$ (...
1
vote
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
votes
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
votes
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
votes
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
votes
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 ...
1
vote
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 ...
