Can anyone clarify Ozonolysis?

[sfoksn]

How can I recognize Ozonolysis as happening in reducing condition or oxidative condition?

I know H2O2 is a big giveaway about oxidative condition, but what other clues can I look for in order to determine the conditions?


Thank you in advance.

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[Vokalyzd]

Ozonolysis always occurs with O3 and it splits alkenes into aldehydes and alkynes into carboxylic acid. Secondary alkenes will be ketones.

 

[sfoksn]

Not necessarily, I thought...

Alkynes can become diketones or carboxylic acids, as far as I remember,

and Alkenes do not always turn into aldehydes. They turn into carboxylic acid as well when ozonolysis is done under oxidative conditions.

My question is, how do we recognize the ozonolysis condition as reductive or oxidative?

Please correct me if I am wrong.
Thank you

 

[Vokalyzd]

From what I remember (took my DAT yesterday) alkenes are split into aldehyde and alkynes are split into carboxylic acid. However, it depends on the subsequent step
I.E.
CH3CH=CHCH3 -O3,CH2Cl2-> 2x CH3COH will be aldehyde but if they do the 1)O3,CH2Cl2 and 2) LAH then the LAH will reduce the aldehyde into an alcohol (nothing to do with ozonolysis). If step 2) CrO3, KMnO4, or any oxidizing agents, the aldehyde will be a carboxylic acid.

for Alkynes you will only reduce it ( NaBH4 won't reduce CA or Esters, LAH will reduce it to a primary alcohol). I hope that cleared it up.

 

[Erhatstil]

How can I recognize Ozonolysis as happening in reducing condition or oxidative condition?

I know H2O2 is a big giveaway about oxidative condition, but what other clues can I look for in order to determine the conditions?


Thank you in advance.

i dont think there many variations for ozonolysis of alkenes. like you said, if H2O2 is present, it's an oxidative work-up and will yield carboxylic acid. if Zn, or S(CH3)2 is present, it's a reducing work-up and will yield the aldehyde.

for alkynes, i think permanganate will form the diketone, while ozonolysis will form 2 carboxylic acids. unless the triple bond is terminal and ozonolysis with form 1 carboxylic acid and CO2.

 

[BruinDentist]

The OChem section of the actual DAT is very basic (at least it was for me), so I don't think you need to concern yourself with secondary reagents. Just get the general idea of the reactions down as Vokalyzd described with ozonolysis.

 

[sfoksn]

Thank you everyone! Very helpful