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Converting a cis-alkene to trans-alkene
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Oleksandr Zginnyk
Converting a cis-alkene to trans-alkene
There are two other methods which I know, if you were to take a cis-1,2-diaryl alkene and expose it to UV light then you will excite the alkene into a 1,2-diradical. The $\ce{C-C}$ single bond in this is free to rotate.
It will then randomly form a $1:1$ mixture of the cis and trans isomers. As the photophysical properties of the two isomers are different (extinction coefficient) it is possible using light of a given wavelength to convert any mixture of cis/trans into a mixture with a given cis/trans ratio. A photostationary mixture. By changing the wavelength the ratio in the mixture changes.
Another method would be to react the cis alkene with a metal hydride which has a vacant coordination site such as $\ce{RuHCl(CO)(PPh3)2}$. Then do a β hydride elimination to form an alkene and the metal hydride again. This relates to the way in which trans fats are formed during the hydrogenation of plant oils (lipids with cis alkenes).
There are two other methods which I know, if you were to take a cis-1,2-diaryl alkene and expose it to UV light then you will excite the alkene into a 1,2-diradical. The $\ce{C-C}$ single bond in this is free to rotate.
It will then randomly form a $1:1$ mixture of the cis and trans isomers. As the photophysical properties of the two isomers are different (extinction coefficient) it is possible using light of a given wavelength to convert any mixture of cis/trans into a mixture with a given cis/trans ratio. A photostationary mixture. By changing the wavelength the ratio in the mixture changes.
Another method would be to react the cis alkene with a metal hydride which has a vacant coordination site such as $\ce{RuHCl(CO)(PPh3)2}$. Then do a β hydride elimination to form an alkene and the metal hydride again. This relates to the way in which trans fats are formed during the hydrogenation of plant oils (lipids with cis alkenes).
Your method looks fine. There is another simple method (with three steps though).
Convert the the cis alkene to a dibromo derivative using bromine;
Use two equivalents of $\ce{NaNH2}$ to get an alkyne (elimination);
Selective reduction to trans alkene by using sodium in liquid ammonia.
However this requires that Hydrogen be present as a substituent on the double bond, on both carbons.
Your method looks fine. There is another simple method (with three steps though).
Convert the the cis alkene to a dibromo derivative using bromine;
Use two equivalents of $\ce{NaNH2}$ to get an alkyne (elimination);
Selective reduction to trans alkene by using sodium in liquid ammonia. However this requires that Hydrogen be present as a substituent on the double bond, on both carbons.
I know that method. Do you have anything else to add about my method?More
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For E/Z trisubstituted alkenes capable of E2 elimination the following sequence may apply. Add the elements of water in a syn, anti-Markovnikov fashion to the double bond. Remove the elements of water as p-toluenesulfonic acid viaanti E2 elimination. The cycle below illustrates this point.
For E/Z trisubstituted alkenes capable of E2 elimination the following sequence may apply. Add the elements of water in a syn, anti-Markovnikov fashion to the double bond. Remove the elements of water as p-toluenesulfonic acid viaanti E2 elimination. The cycle below illustrates this point.
There are two other methods which I know, if you were to take a cis-1,2-diaryl alkene and expose it to UV light then you will excite the alkene into a 1,2-diradical. The $\ce{C-C}$ single bond in this is free to rotate.
It will then randomly form a $1:1$ mixture of the cis and trans isomers. As the photophysical properties of the two isomers are different (extinction coefficient) it is possible using light of a given wavelength to convert any mixture of cis/trans into a mixture with a given cis/trans ratio. A photostationary mixture. By changing the wavelength the ratio in the mixture changes.
Another method would be to react the cis alkene with a metal hydride which has a vacant coordination site such as $\ce{RuHCl(CO)(PPh3)2}$. Then do a β hydride elimination to form an alkene and the metal hydride again. This relates to the way in which trans fats are formed during the hydrogenation of plant oils (lipids with cis alkenes).
There are two other methods which I know, if you were to take a cis-1,2-diaryl alkene and expose it to UV light then you will excite the alkene into a 1,2-diradical. The $\ce{C-C}$ single bond in this is free to rotate.
It will then randomly form a $1:1$ mixture of the cis and trans isomers. As the photophysical properties of the two isomers are different (extinction coefficient) it is possible using light of a given wavelength to convert any mixture of cis/trans into a mixture with a given cis/trans ratio. A photostationary mixture. By changing the wavelength the ratio in the mixture changes.
Another method would be to react the cis alkene with a metal hydride which has a vacant coordination site such as $\ce{RuHCl(CO)(PPh3)2}$. Then do a β hydride elimination to form an alkene and the metal hydride again. This relates to the way in which trans fats are formed during the hydrogenation of plant oils (lipids with cis alkenes).
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Your method looks fine. There is another simple method (with three steps though).
However this requires that Hydrogen be present as a substituent on the double bond, on both carbons.
Your method looks fine. There is another simple method (with three steps though).
However this requires that Hydrogen be present as a substituent on the double bond, on both carbons.
More
VOTE
VOTE
For E/Z trisubstituted alkenes capable of E2 elimination the following sequence may apply. Add the elements of water in a syn, anti-Markovnikov fashion to the double bond. Remove the elements of water as p-toluenesulfonic acid via anti E2 elimination. The cycle below illustrates this point.
For E/Z trisubstituted alkenes capable of E2 elimination the following sequence may apply. Add the elements of water in a syn, anti-Markovnikov fashion to the double bond. Remove the elements of water as p-toluenesulfonic acid via anti E2 elimination. The cycle below illustrates this point.
More
VOTE