[iScience]

in one youtube video, they say that the pi electrons attack the neutral Oxygen of O₃ and in another video they say that the oxygen with the negative formal charge attacks one of the carbons.

which video is correct? and why is that video correct and the other video wrong?

[discodermolide]

I think it's the pi electrons attacking the oxygen and eliminating O₂. A negative charge cannot easily approach an electron rich pi cloud.

[zsinger]

Disco is correct.  Too much electron density in a Pi bond certainly. 

[iScience]

can you guys refer me to something more quantitative? when we're doing reactions in my o chem class, he draws all these arrows but i have no idea why some of these reactions are initiated. maybe there's a formula describing whether or not a reaction will occur when two compounds/atoms are brought together?

[PhDoc]

First of all, please get away from YouTube for anything not related to high school. Although there are some good videos out there, it's easy for an academic to pull out egregious errors in each video. Remember, you can try to explain to your prof how "YouTube said it was right," but your prof is guaranteed to tell you "YouTube is not grading your exam."

An ozonolysis reaction is an example of a 1,3-dipolar cycloaddition (+ reverse cycloaddition + re-cycloaddition) which may be thought of as a concerted process (all bond making and breaking steps occurring simultaneously). A stepwise diradical mechanism was once proposed, however there is too much evidence to support the cycloaddition mechanism. This reaction takes place via a six-electron aromatic transition state.

http://lennoxtutoring.com/2012/09/04/ozonolysis-mechanism/

O2 is not eliminated from this reaction. Rather a reductant (Me2S or Zn) extrudes an oxygen atom to complete the process.

Please look up 1,3-dipolar cycloadditions in a good textbook such as Vollhardt or Streitwieser and Heathcock, however a more rigorous explanation may be found here:

http://www.chem.wisc.edu/areas/organic/studsemin/wilde/wilde-sem.pdf