Why can single bonds rotate?

Because the orbitals that form ##sigma## bonds are totally symmetric about the internuclear axis, and the properties of vector addition and scalar multiplication of these orbitals is preserved during the bond rotation.

The rotation of a particular single bond does not change the identity of the orbital in question used to make the bond, so the bond itself does not change.

That means we still retain the same molecule after a full ##360^@## rotation of the bond as follows:

(Note that rotating double bonds is not possible, and rotating an entire molecule about the internuclear axis is not rotating the bond, but the molecule itself, which doesn’t count in any case.)

SINGLE BONDS IN RELATION TO HEAD-ON ORBITAL OVERLAP

Single bonds are really the result of one sigma (##sigma##) bond.

So, let’s consider two orbitals that are capable of overlapping head-on to generate a ##sigma## bond via a linear combination of atomic orbitals (LCAO):

where ##sigma_(2p_z)## is the molecular orbital that formed from the linear combination of the two ##2p_z## atomic orbitals.

ORBITAL SYMMETRY DICTATES ABILITY TO ROTATE THE BOND

You can see that rotating one of these orbitals about the internuclear axis (the ##z## axis) does not change their look at all because they are totally symmetric about the ##z## axis.

This is an important feature of a ##sigma## bond, because if the orbital looks different upon rotation about the internuclear axis, it would not be what is known as a linear transformation.

A linear transformation preserves the properties of vector addition and scalar multiplication.

This may seem trivial, but it ensures that the two orbitals can continue overlapping as they have been in a LCAO and generate the same molecular orbital upon that overlap.

(It’s one of those “do I really need to care” moments in chemistry, but that’s the true reason why.)

CONCLUSION

Overall…

If we rotate a single bond about the internuclear axis, if either orbital participating in the bond becomes a different orbital (such as a ##2p_x## vs. a ##2p_y## orbital), then we are either looking at a different bond or the bond doesn’t exist.







Calculate Your Essay Price
(550 words)

Approximate price: $22

Calculate the price of your order

550 words
We'll send you the first draft for approval by September 11, 2018 at 10:52 AM
Total price:
$26
The price is based on these factors:
Academic level
Number of pages
Urgency
Basic features
  • Free title page and bibliography
  • Unlimited revisions
  • Plagiarism-free guarantee
  • Money-back guarantee
  • 24/7 support
On-demand options
  • Writer’s samples
  • Part-by-part delivery
  • Overnight delivery
  • Copies of used sources
  • Expert Proofreading
Paper format
  • 275 words per page
  • 12 pt Arial/Times New Roman
  • Double line spacing
  • Any citation style (APA, MLA, Chicago/Turabian, Harvard)

Our guarantees

Delivering a high-quality product at a reasonable price is not enough anymore.
That’s why we have developed 5 beneficial guarantees that will make your experience with our service enjoyable, easy, and safe.

Money-back guarantee

You have to be 100% sure of the quality of your product to give a money-back guarantee. This describes us perfectly. Make sure that this guarantee is totally transparent.

Read more

Zero-plagiarism guarantee

Each paper is composed from scratch, according to your instructions. It is then checked by our plagiarism-detection software. There is no gap where plagiarism could squeeze in.

Read more

Free-revision policy

Thanks to our free revisions, there is no way for you to be unsatisfied. We will work on your paper until you are completely happy with the result.

Read more

Privacy policy

Your email is safe, as we store it according to international data protection rules. Your bank details are secure, as we use only reliable payment systems.

Read more

Fair-cooperation guarantee

By sending us your money, you buy the service we provide. Check out our terms and conditions if you prefer business talks to be laid out in official language.

Read more

Order your essay today and save 10% with the coupon code: best10