Why does C-C have a higher bond energy than B-N in hBN and graphene?

In summary, the thermal conductivity difference is almost entirely because of the electrical conductivity difference.
  • #1
james weaver
28
4
Hi everyone, this is my first post in the chemistry section. I am doing a project for my engineering class on "cutting edge" materials and the one I chose is hexagonal boron nitride (specifically in the form of nanotubes). In comparing hBN to graphene, I need to explain to the class why graphene has a much higher thermal conductivity. From what I've read, non-metals transfer heat via vibrations in their lattice structures. As I understand it, atoms with higher bond energies have a stiffer spring-like effect which enables them to transfer heat quicker (makes sense because B-N has lower bond energy than C-C). My question is this:

Why does C-C have a higher bond energy than B-N? I thought that non-polar bonds in general have lower bond energies, and this case C-C has the less polar bond but higher bond energy.
 
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  • #3
DrClaude said:
The carbon-carbon bonds in graphene are double bonds and the electrons are delocalized over many carbon atoms
hBN seems to be isoelectronic with graphene, which suggests bonds of a comparable strength, doesn't it?
 
  • #4
Borek said:
hBN seems to be isoelectronic with graphene, which suggests bonds of a comparable strength, doesn't it?
Good point. But the bonds are highly polar.
 
  • #5
The bond strength in hBN is similar to that of graphene. The thermal conductivity difference is almost entirely because of the electrical conductivity difference.

Thermal conductivity in general is determined by propagation of energy through the lattice, in the form of either phonons or electrons. hBN and graphene have similar phonon spectra, but hBN is an electrical insulator, whereas graphene is an electrical conductor, so electrons contribute substantially to the thermal conductivity in graphene but not hBN.
 
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Related to Why does C-C have a higher bond energy than B-N in hBN and graphene?

1. What is the difference between the bond strength of B-N and C-C?

The bond strength of B-N and C-C refers to the amount of energy required to break the bond between the atoms of boron and nitrogen, and carbon and carbon, respectively. The main difference between these two bonds is due to the electronegativity of the atoms involved. Boron and nitrogen have a higher electronegativity difference compared to carbon and carbon, resulting in a stronger bond between B-N.

2. Which bond is stronger, B-N or C-C?

The B-N bond is generally considered to be stronger than the C-C bond due to the higher electronegativity difference between boron and nitrogen. However, the strength of a bond can also depend on other factors such as bond length and molecular structure.

3. What factors affect the bond strength of B-N and C-C?

The bond strength of B-N and C-C can be affected by several factors, including electronegativity difference, bond length, and molecular structure. Additionally, the presence of other atoms or functional groups in the molecule can also influence the bond strength.

4. How does the bond strength of B-N and C-C affect the properties of molecules?

The bond strength of B-N and C-C can greatly impact the properties of molecules. For example, molecules with stronger B-N bonds tend to have higher melting and boiling points, as well as greater stability. In contrast, molecules with weaker C-C bonds may have lower melting and boiling points and be more reactive.

5. Can the bond strength of B-N and C-C be manipulated?

Yes, the bond strength of B-N and C-C can be manipulated through various methods such as changing the electronegativity of the atoms involved, altering the bond length, or introducing different functional groups. These manipulations can result in changes in the properties and reactivity of molecules.

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