Question

I need to prepare butanoic acid from ethene, I made up the first steps. But then I have to make propene from ethene, How do I do that? http://puu.sh/5uSSY.png

Answer 1

there are a few ways to extend carbon chains, the most common are grignard reagents, or witting reagents.

Answer 2

wittig*

Answer 3

My book has only 2 formulas for grignard reactants (and thats it no more information): RCHO + R'MgBr + H2O ---> R-CHOH-R' + MgBROH and also the same one but for ketones. If I use this formula. I could get the propanol molecule in my exercise by doing this: http://puu.sh/5vbAS.png , But the problem is that We get a grignard reactant CH3BrMg , but we cant make that from ethene, I havent seen that yet.

Answer 4

Get ethene, brominate it, add Mg metal.
in another container, get ethene, make ethanol, oxidize it to a an aldehyde.

mix the 2, you'll end up with 2 butanol

Answer 5

this has to be in a non-aqueous medium

Answer 6

be done*

Answer 7

I think we get 3 butanol. Am I right? But if we get 3 butanol, how do we get butanoic acid from it? We can only convert primary alcohols to carboxylic acids. Secondary alcohols convert into ketones!

Answer 8

oh actually we do not get butanol from those 2, we get pentanol!

Answer 9

2 butanol and 3 butanol is the same molecule, but recall we always name it with the lowest number possible.

once you get 2 butanol, dehydrate it, then add an alcohol with hydroboration (least substituted carbons), then oxidize it to an acid

Answer 10

no it isnt butanol that we get

Answer 11

nope, thats impossible. how do you get a 5 carbon chain when both of your reactants were 2 carbon chains.

Answer 12

when I dehydrate I can get 2 possibilities, are they both possible? --> http://puu.sh/5vdKQ.png

Answer 13

yeah unfortunately.

Answer 14

thats good; I will do this is this ok aaronq: http://puu.sh/5velM.png

Answer 15

yeah sounds good. it works on paper, but in real life you'd get a crappy yield

Answer 16

yes finally thank you aroonq, I spend all day trying to solve it. You just saved lots of my time. Thank you so much!

Answer 17

no problem dude, you should check out this website, you'll learn a lot from the synthesis questions.

http://highered.mcgraw-hill.com/classware/ala.do?isbn=0073047872&alaid=ala_964364&showSelfStudyTree=true

Answer 18

ok thank you!!