Topic: By looking at a reaction, how can you tell whether it is convergent or linear? (Read 5100 times)

alis88 · « **on:** February 22, 2009, 04:45:53 AM »

I am struggling to tell if a synthesis is convergent or not, simply by looking at the reaction written down.

Can someone please help me?

Thanks

Alis

sjb · « **Reply #1 on:** February 22, 2009, 07:57:44 AM »

Consider, for example http://en.wikipedia.org/w/index.php?title=Convergent_synthesis&oldid=269095340 ?

S

alis88 · « **Reply #2 on:** February 23, 2009, 03:52:58 AM »

Thanks S.

I understand that - I understand that in linear synthesis, the yield drops rapidly with each reaction step. In convergent synthesis, there will be a greater yield.

However, not sure how to apply it to certain reactions...

If anyone could explain further, that would be helpful.

Thank you.

Alis

alexjaco · « **Reply #3 on:** February 23, 2009, 09:08:15 AM »

Convergent just means you make two "advanced" intermediates and react them together at some point beyond the first step

alis88 · « **Reply #4 on:** February 23, 2009, 09:48:59 AM »

Thanks alexjaco, that's very helpful.

Can you please clarify what you mean by "advanced?"

Alis

alexjaco · « **Reply #5 on:** February 23, 2009, 10:33:57 AM »

Basically, beyond the first step or a few steps in, but a lot of synthetic chemists will plan on "converging" their advanced intermediates as many steps into the synthesis as possible, but thats not always possible.

alexjaco · « **Reply #6 on:** February 23, 2009, 10:50:52 AM »

I guess to help you a little more, the synthesis would be convergent if two compounds are made separately and then reacted together to make a new product. If it we linear, it would just be step after step after step, no combination of two things made separately.

macman104 · « **Reply #7 on:** February 23, 2009, 11:46:54 AM »

This is how my professor explained convergent or linear.

If you want to build up a C₁₆ carbon skeleton (that means a carbon skeleton 10 carbons long in case you aren't familiar with that notation):

Convergent:

C₂ + C₂ = C₄
C₄ + C₄ = C₈
C₈ + C₈ = C₁₆

Linear:

C₂ + C₂ = C₄
C₄ + C₂ = C₆
C₆ + C₂ = C₈
C₈ + C₂ = C₁₀
C₁₀ + C₂ = C₁₂
C₁₂ + C₂ = C₁₄
C₁₄ + C₂ = C₁₆

Mind you, this is a highly, highly simplified example, but it should help illustrate the idea. You may separately build up two different C4 skeletons and then combine them, instead of slowly building up the chain, bit by bit.

alis88 · « **Reply #8 on:** February 24, 2009, 05:30:51 AM »

Thank you so much macman104 and alexjaco - I feel I understand the concept a lot better now.

Topic: By looking at a reaction, how can you tell whether it is convergent or linear? (Read 5100 times)

alis88

By looking at a reaction, how can you tell whether it is convergent or linear?

sjb

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

alis88

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

alexjaco

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

alis88

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

alexjaco

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

alexjaco

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

macman104

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

alis88

Re: By looking at a reaction, how can you tell whether it is convergent or linear?

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