Exploring Dipole Moment of Halomethanes in Organic Chemistry

In summary, the structure of alkyl halides, specifically radical halogenation, is discussed in an organic chemistry text. A table of halomethanes provides information on bond length, bond strength, and dipole moment. The dipole moment is expressed in Debye's (D) and can be measured but may be difficult to calculate accurately. The numbers can be used to compare the relative ranking of the halomethanes. This information can be found in "Organic Chemistry, 7th Edition, McMurry" on page 335. The question posed is not a homework assignment, but a concept question.
  • #1
study.bug
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I'm reading in my organic chemistry text about the structure of alkyl halides, as a background to why certain reactions happen (specifically radical halogenation). In it there's a table of halomethanes, that tells the bond length, bond strength, and dipole moment. It pretty much looks like this:

Fluoromethane Bond length 136pm, Bond strength 108 kcal/mol, Dipole moment (D) 1.85
Bromomethane Bond length 178pm, Bond strength 84 kcal/mol, Dipole moment (D) 1.87
Chloromethane Bond length 193pm, Bond strength 70 kcal/mol, Dipole moment (D) 1.81
Iodomethane Bond length 214pm, Bond strength 56 kcal/mol, Dipole moment (D) 1.62

I understand what's going on with the dipole moment, but exactly what does it mean to have a Dipole moment of 1.85? Also, can these numbers be calculated to compared each other?

If you're curious, this is from the text "Organic Chemistry, 7th Edition, McMurry", page 335. And this is NOT a homework assignment, just a concept question. =)
 
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  • #2
study.bug said:
I'm reading in my organic chemistry text about the structure of alkyl halides, as a background to why certain reactions happen (specifically radical halogenation). In it there's a table of halomethanes, that tells the bond length, bond strength, and dipole moment. It pretty much looks like this:

Fluoromethane Bond length 136pm, Bond strength 108 kcal/mol, Dipole moment (D) 1.85
Bromomethane Bond length 178pm, Bond strength 84 kcal/mol, Dipole moment (D) 1.87
Chloromethane Bond length 193pm, Bond strength 70 kcal/mol, Dipole moment (D) 1.81
Iodomethane Bond length 214pm, Bond strength 56 kcal/mol, Dipole moment (D) 1.62

I understand what's going on with the dipole moment, but exactly what does it mean to have a Dipole moment of 1.85? Also, can these numbers be calculated to compared each other?

If you're curious, this is from the text "Organic Chemistry, 7th Edition, McMurry", page 335. And this is NOT a homework assignment, just a concept question. =)

The 1.85 is expressed in Debye's (D). Good Google term. Measurement is... challenging. The numbers are measured. I'm not sure if you can calculate it accurately but you may be able to calculate a relative ranking.
 

1. What is a dipole moment?

A dipole moment is a measure of the separation of positive and negative charges within a molecule. It is represented by a vector, with the direction pointing from the positive end to the negative end of the molecule.

2. How do halomethanes exhibit dipole moments?

Halomethanes, also known as haloalkanes, contain a carbon atom bonded to one or more halogen atoms (fluorine, chlorine, bromine, or iodine). These halogen atoms have a higher electronegativity than carbon, causing a permanent dipole moment to form between the two atoms.

3. Why is the dipole moment of halomethanes important in organic chemistry?

The dipole moment of a molecule affects its physical and chemical properties. In organic chemistry, it is particularly important for understanding the polarity of a molecule, its reactivity, and its interactions with other molecules.

4. How is the dipole moment of halomethanes measured?

The dipole moment of a molecule can be experimentally determined using techniques such as nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography. Theoretical methods, such as quantum mechanical calculations, can also be used to predict the dipole moment of a molecule.

5. What factors can affect the dipole moment of halomethanes?

The dipole moment of a halomethane can be influenced by the size and electronegativity of the halogen atom, as well as the geometry of the molecule. For example, a molecule with a more linear shape will have a larger dipole moment compared to a molecule with a more bent shape.

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