Kaplan GC OC subject tests questions

[Emmie]

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subject test 3

#5) Addition of Br2 to 2-pentene yields dibromopentane

syn or anti addition?

#7)

If you add concentrated KMnO4 to propene, will you get carboxylic acid?

 

[nze82]

Addition of Br2 to 2-pentene yields dibromopentane

syn or anti addition?

Anti

 

[Emmie]

that's what I thought but the ans key said syn, and I'm confused.

 

[nze82]

that's what I thought but the ans key said syn, and I'm confused.

Dunno then, I always thought addition of halides across the double bond is an anti addition.

 

[imbenis]

anti

for #7 you should get ethanoic acid and CO2 under conditions with warm concentrated and acidic kmno4, if it is cold and dilute you will get a gem-diol (syn), a reaction very similar to OsO4

 

[sixkiller]

that's what I thought but the ans key said syn, and I'm confused.

It's sort of a trick....

Yes, it is indeed anti....

Draw it out as you would with the anti product. Now draw the conformers and you will get the correct answer.

Also keep in mind that there is also the enantiomer.

This is sort of a trick question to expose "trigger happy/recall" responses.

 

[Emmie]

the ans key said the ans is syn. Imbenis' picture isn't for that particular question (thx for taking the time to post it BTW). oh well, I vote for anti.

 

[Emmie]

anti

for #7 you should get ethanoic acid and CO2 under conditions with warm concentrated and acidic kmno4, if it is cold and dilute you will get a gem-diol (syn), a reaction very similar to OsO4

on the answer key (probably wrong), it said that propene and ethane are both turn into carboxylic acid under conc. KMnO4 which doesn't make sense to me. Could you please post that particular question? thx.