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Temas de Química Orgánica - Enantiómeros y nomenclatura R-S
- 1. Temas de Química Orgánica Enantiómeros y nomenclatura R/S
- 2. triplenlace.com Considérese este compuesto. El átomo central (negro) es un C. Los demás son cuatro sustituyentes cualesquiera. (Obsérvese que dos sustituyentes son iguales)
- 3. triplenlace.com Sean las estructuras A y B; consideremos si corresponden a compuestos diferentes
- 4. Imágenes especulares triplenlace.com No es difícil comprobar que ambas estructuras son imágenes especulares la una de la otra
- 5. Imágenes especulares triplenlace.com Para compararlas mejor, copiaremos la estructura A debajo, manteniendo la posición de sus átomos…
- 6. Imágenes especulares 120º triplenlace.com …y a la B le daremos un giro de 120º
- 8. Imágenes especulares superponibles triplenlace.com Si se pone una estrucutra sobre la otra, ambas quedarán superpuestas. Se dice que las dos imágenes especulares dibujadas inicialmente son superponibles. En realidad, A y B son imágenes del mismo compuesto
- 9. triplenlace.com Supongamos ahora la estructura X, que representa a un compuesto que tiene un C con cuatro sustituyentes distintos. Consideremos al mismo tiempo la estructura Y, que es imagen especular de la X X Y
- 12. Imágenes especulares 120º triplenlace.com Si giramos 120º la estructura Y y una vez girada la ponemos bajo la original… X Y
- 13. no superponibles Imágenes especulares triplenlace.com podremos comprobar que el resultado no es superponible a la estructura X X Y
- 14. no superponibles Imágenes especulares triplenlace.com En ese caso, se dice que X e Y representan a dos moléculas distintas. Aunque parezcan iguales, el simple hecho de que la orientación espacial relativa de los sustituyentes del C central sea diferente, les confiere propiedades diferentes. Desde luego, son isómeros entre sí, pues tienen los mismos átomos. Se dice que son isómeros ópticos o enantiómeros X Y X e Y son enantiómeros
- 15. triplenlace.com Un compuesto (u objeto) se dice que es quiral cuando no es superponible con su imagen en un espejo Quiralidad
- 16. triplenlace.com Si un compuesto tiene un plano de simetría no es quiral porque se puede superponer con su imagen en un espejo (recordemos el compuesto A de antes) A Quiralidad
- 17. Quiralidad Aquiral Tiene plano de simetría triplenlace.com
- 18. Aquiral Tiene plano de simetría Quiralidad triplenlace.com Pero si no tiene plano de simetría es quiral
- 19. Aquiral Tiene plano de simetría Quiralidad Quiral No tiene plano de simetría triplenlace.com
- 20. espejo Quiralidad Quiral X no es superponible con su imagen especular Y triplenlace.com X Y No tiene plano de simetría
- 21. Quiralidad Quiral X e Y son enantiómeros triplenlace.com espejoX Y No tiene plano de simetría
- 22. Quiralidad Quiral X e Y son enantiómeros triplenlace.com espejoX Y No tiene plano de simetría Los enantiómeros se dice que tienen actividad óptica porque desvían el plano de la luz polarizada. Dados dos enantióméros como X e Y, uno desvía el plano de la luz polarizada en un sentido y el otro en el otro sentido.
- 23. Quiralidad Quiral X e Y son enantiómeros triplenlace.com espejoX Y No tiene plano de simetríaNota: los estereoisómeros que no son enantiómeros, o sea, que no son imágenes especulares entre sí, se llaman diastereoisómeros
- 24. Ejemplo de enantiómeros Butan-2-ol triplenlace.com Un C con cuatro sustituyentes distintos se dice que es quiral
- 25. Ejemplo de enantiómeros Butan-2-ol triplenlace.com Una molécula con un solo C quiral es quiral. Si tiene más de un C, puede ser aquiral o quiral, dependiendo de que tenga o no plano de simetría
- 26. Butan-2-ol espejo Ejemplo de enantiómeros triplenlace.com Estas dos moléculas son enantiomeros entre sí
- 27. Nomenclatura R/S triplenlace.com Para distinguir entre dos enantiómeros usamos la nomenclarura R/S
- 28. Nomenclatura R/S triplenlace.com Se numeran los sustituyentes de mayor a menor prioridad (la prioridad la da el número atómico; en caso de coincidencia, el número atómico de los siguientes átomos en cada cadena)
- 29. Nomenclatura R/S triplenlace.com Se mira la molécula de modo que el sustituyente con menos prioridad quede lo más lejos posible del observador
- 30. Nomenclatura R/S triplenlace.com Se traza un arco desde el sustituyente 1 al 3 pasando por el 2
- 31. Nomenclatura R/S triplenlace.com Si el sentido del arco es contrario al de las agujas del reloj, el enantiómero es S (del latín sinister, izquierda)
- 32. Nomenclatura R/S triplenlace.com Si el sentido del arco es el de las agujas del reloj, el enantiómero es R (del latín rectus, derecha)
- 35. Butan-2-ol espejo 1 2 3 4 4 1 2 3 (S)-bután-2-ol (S)-bután-2-ol Nomenclatura R/S triplenlace.com
- 36. Butan-2-ol espejo 1 2 3 4 4 1 2 3 (S)-bután-2-ol (R)-bután-2-ol Nomenclatura R/S triplenlace.com
- 37. Temas del Curso Básico de Química Orgánica http://triplenlace.com/cbqo/ Más…
- 38. Problemas del Curso Básico de Química Orgánica http://triplenlace.com/problemas-de- principales-compuestos-organicos/ Más…
Notas del editor
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- Optical isomerism is a form of stereoisomerism. In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement. Optical isomerism is one form of stereoisomerism. Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light. Simple substances which show optical isomerism exist as two isomers known as enantiomers. Simple substances which show optical isomerism exist as two isomers known as enantiomers. A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form. For example, one of the optical isomers (enantiomers) of the amino acid alanine is known as (+)alanine. A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form. So the other enantiomer of alanine is known as or (-)alanine. If the solutions are equally concentrated the amount of rotation caused by the two isomers is exactly the same - but in opposite directions. When optically active substances are made in the lab, they often occur as a 50/50 mixture of the two enantiomers. This is known as a racemic mixture or racemate. It has no effect on plane polarised light.
- La reacción SN2 (conocida también como sustitución nucleofílica bimolecular o como ataque desde atrás) es un tipo de sustitución nucleofílica, donde un par libre de un nucleófilo ataca un centro electrofílico y se enlaza a él, expulsando otro grupo denominado grupo saliente. En consecuencia, el grupo entrante reemplaza al grupo saliente en una etapa. Dado que las dos especies reaccionantes están involucradas en esta etapa limitante lenta de la reacción química, esto conduce al nombre de sustitución nucleofílica bimolecular, o SN2. Entre los químicos inorgánicos, la reacción SN2 es conocida frecuentemente como el mecanismo de intercambio. La reacción SN1 es una reacción de sustitución en química orgánica. "SN" indica que es una sustitución nucleofílica y el "1" representa el hecho de que la etapa limitante es unimolecular.1 2 La reacción involucra un intermediario carbocatión y es observada comúnmente en reacciones de halogenuros de alquilo secundarios o terciarios, o bajo condiciones fuertemente acídicas, con alcoholes secundarios y terciarios. Con los halogenuros de alquilo primarios, sucede la reacción SN2, alternativa. Entre los químicos inorgánicos, la reacción SN1 es conocida frecuentemente como el mecanismo disociativo. Un mecanismo de reacción fue propuesto por primera vez por Christopher Ingold y colaboradores en 1940.3
- La reacción SN2 (conocida también como sustitución nucleofílica bimolecular o como ataque desde atrás) es un tipo de sustitución nucleofílica, donde un par libre de un nucleófilo ataca un centro electrofílico y se enlaza a él, expulsando otro grupo denominado grupo saliente. En consecuencia, el grupo entrante reemplaza al grupo saliente en una etapa. Dado que las dos especies reaccionantes están involucradas en esta etapa limitante lenta de la reacción química, esto conduce al nombre de sustitución nucleofílica bimolecular, o SN2. Entre los químicos inorgánicos, la reacción SN2 es conocida frecuentemente como el mecanismo de intercambio. La reacción SN1 es una reacción de sustitución en química orgánica. "SN" indica que es una sustitución nucleofílica y el "1" representa el hecho de que la etapa limitante es unimolecular.1 2 La reacción involucra un intermediario carbocatión y es observada comúnmente en reacciones de halogenuros de alquilo secundarios o terciarios, o bajo condiciones fuertemente acídicas, con alcoholes secundarios y terciarios. Con los halogenuros de alquilo primarios, sucede la reacción SN2, alternativa. Entre los químicos inorgánicos, la reacción SN1 es conocida frecuentemente como el mecanismo disociativo. Un mecanismo de reacción fue propuesto por primera vez por Christopher Ingold y colaboradores en 1940.3
- La reacción SN2 (conocida también como sustitución nucleofílica bimolecular o como ataque desde atrás) es un tipo de sustitución nucleofílica, donde un par libre de un nucleófilo ataca un centro electrofílico y se enlaza a él, expulsando otro grupo denominado grupo saliente. En consecuencia, el grupo entrante reemplaza al grupo saliente en una etapa. Dado que las dos especies reaccionantes están involucradas en esta etapa limitante lenta de la reacción química, esto conduce al nombre de sustitución nucleofílica bimolecular, o SN2. Entre los químicos inorgánicos, la reacción SN2 es conocida frecuentemente como el mecanismo de intercambio. La reacción SN1 es una reacción de sustitución en química orgánica. "SN" indica que es una sustitución nucleofílica y el "1" representa el hecho de que la etapa limitante es unimolecular.1 2 La reacción involucra un intermediario carbocatión y es observada comúnmente en reacciones de halogenuros de alquilo secundarios o terciarios, o bajo condiciones fuertemente acídicas, con alcoholes secundarios y terciarios. Con los halogenuros de alquilo primarios, sucede la reacción SN2, alternativa. Entre los químicos inorgánicos, la reacción SN1 es conocida frecuentemente como el mecanismo disociativo. Un mecanismo de reacción fue propuesto por primera vez por Christopher Ingold y colaboradores en 1940.3
- La reacción SN2 (conocida también como sustitución nucleofílica bimolecular o como ataque desde atrás) es un tipo de sustitución nucleofílica, donde un par libre de un nucleófilo ataca un centro electrofílico y se enlaza a él, expulsando otro grupo denominado grupo saliente. En consecuencia, el grupo entrante reemplaza al grupo saliente en una etapa. Dado que las dos especies reaccionantes están involucradas en esta etapa limitante lenta de la reacción química, esto conduce al nombre de sustitución nucleofílica bimolecular, o SN2. Entre los químicos inorgánicos, la reacción SN2 es conocida frecuentemente como el mecanismo de intercambio. La reacción SN1 es una reacción de sustitución en química orgánica. "SN" indica que es una sustitución nucleofílica y el "1" representa el hecho de que la etapa limitante es unimolecular.1 2 La reacción involucra un intermediario carbocatión y es observada comúnmente en reacciones de halogenuros de alquilo secundarios o terciarios, o bajo condiciones fuertemente acídicas, con alcoholes secundarios y terciarios. Con los halogenuros de alquilo primarios, sucede la reacción SN2, alternativa. Entre los químicos inorgánicos, la reacción SN1 es conocida frecuentemente como el mecanismo disociativo. Un mecanismo de reacción fue propuesto por primera vez por Christopher Ingold y colaboradores en 1940.3
- La reacción SN2 (conocida también como sustitución nucleofílica bimolecular o como ataque desde atrás) es un tipo de sustitución nucleofílica, donde un par libre de un nucleófilo ataca un centro electrofílico y se enlaza a él, expulsando otro grupo denominado grupo saliente. En consecuencia, el grupo entrante reemplaza al grupo saliente en una etapa. Dado que las dos especies reaccionantes están involucradas en esta etapa limitante lenta de la reacción química, esto conduce al nombre de sustitución nucleofílica bimolecular, o SN2. Entre los químicos inorgánicos, la reacción SN2 es conocida frecuentemente como el mecanismo de intercambio. La reacción SN1 es una reacción de sustitución en química orgánica. "SN" indica que es una sustitución nucleofílica y el "1" representa el hecho de que la etapa limitante es unimolecular.1 2 La reacción involucra un intermediario carbocatión y es observada comúnmente en reacciones de halogenuros de alquilo secundarios o terciarios, o bajo condiciones fuertemente acídicas, con alcoholes secundarios y terciarios. Con los halogenuros de alquilo primarios, sucede la reacción SN2, alternativa. Entre los químicos inorgánicos, la reacción SN1 es conocida frecuentemente como el mecanismo disociativo. Un mecanismo de reacción fue propuesto por primera vez por Christopher Ingold y colaboradores en 1940.3
- La reacción SN2 (conocida también como sustitución nucleofílica bimolecular o como ataque desde atrás) es un tipo de sustitución nucleofílica, donde un par libre de un nucleófilo ataca un centro electrofílico y se enlaza a él, expulsando otro grupo denominado grupo saliente. En consecuencia, el grupo entrante reemplaza al grupo saliente en una etapa. Dado que las dos especies reaccionantes están involucradas en esta etapa limitante lenta de la reacción química, esto conduce al nombre de sustitución nucleofílica bimolecular, o SN2. Entre los químicos inorgánicos, la reacción SN2 es conocida frecuentemente como el mecanismo de intercambio. La reacción SN1 es una reacción de sustitución en química orgánica. "SN" indica que es una sustitución nucleofílica y el "1" representa el hecho de que la etapa limitante es unimolecular.1 2 La reacción involucra un intermediario carbocatión y es observada comúnmente en reacciones de halogenuros de alquilo secundarios o terciarios, o bajo condiciones fuertemente acídicas, con alcoholes secundarios y terciarios. Con los halogenuros de alquilo primarios, sucede la reacción SN2, alternativa. Entre los químicos inorgánicos, la reacción SN1 es conocida frecuentemente como el mecanismo disociativo. Un mecanismo de reacción fue propuesto por primera vez por Christopher Ingold y colaboradores en 1940.3 En química, un epímero es un estereoisómero de otro compuesto que tiene una configuración diferente en uno solo de sus centros estereogénicos. Cuando se incorpora un epímero a una estructura en anillo, es llamado anómero.
- A molecule which has no plane of symmetry is described as chiral. The carbon atom with the four different groups attached which causes this lack of symmetry is described as a chiral centre or as an asymmetric carbon atom. The molecule on the left above (with a plane of symmetry) is described as achiral. Only chiral molecules have optical isomers.
- A molecule which has no plane of symmetry is described as chiral. The carbon atom with the four different groups attached which causes this lack of symmetry is described as a chiral centre or as an asymmetric carbon atom. The molecule on the left above (with a plane of symmetry) is described as achiral. Only chiral molecules have optical isomers.
- A molecule which has no plane of symmetry is described as chiral. The carbon atom with the four different groups attached which causes this lack of symmetry is described as a chiral centre or as an asymmetric carbon atom. The molecule on the left above (with a plane of symmetry) is described as achiral. Only chiral molecules have optical isomers.
- A molecule which has no plane of symmetry is described as chiral. The carbon atom with the four different groups attached which causes this lack of symmetry is described as a chiral centre or as an asymmetric carbon atom. The molecule on the left above (with a plane of symmetry) is described as achiral. Only chiral molecules have optical isomers.
- A molecule which has no plane of symmetry is described as chiral. The carbon atom with the four different groups attached which causes this lack of symmetry is described as a chiral centre or as an asymmetric carbon atom. The molecule on the left above (with a plane of symmetry) is described as achiral. Only chiral molecules have optical isomers.
- One of the enantiomers is simply a non-superimposable mirror image of the other one. In other words, if one isomer looked in a mirror, what it would see is the other one. The two isomers (the original one and its mirror image) have a different spatial arrangement, and so can't be superimposed on each other. If an achiral molecule (one with a plane of symmetry) looked in a mirror, you would always find that by rotating the image in space, you could make the two look identical. It would be possible to superimpose the original molecule and its mirror image. Definición (Wikipedia): A chiral molecule /ˈkaɪərəl/ is a type of molecule that lacks an internal plane of symmetry and thus has a non-superposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom
- One of the enantiomers is simply a non-superimposable mirror image of the other one. In other words, if one isomer looked in a mirror, what it would see is the other one. The two isomers (the original one and its mirror image) have a different spatial arrangement, and so can't be superimposed on each other. If an achiral molecule (one with a plane of symmetry) looked in a mirror, you would always find that by rotating the image in space, you could make the two look identical. It would be possible to superimpose the original molecule and its mirror image. Definición (Wikipedia): A chiral molecule /ˈkaɪərəl/ is a type of molecule that lacks an internal plane of symmetry and thus has a non-superposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom
- One of the enantiomers is simply a non-superimposable mirror image of the other one. In other words, if one isomer looked in a mirror, what it would see is the other one. The two isomers (the original one and its mirror image) have a different spatial arrangement, and so can't be superimposed on each other. If an achiral molecule (one with a plane of symmetry) looked in a mirror, you would always find that by rotating the image in space, you could make the two look identical. It would be possible to superimpose the original molecule and its mirror image. Definición (Wikipedia): A chiral molecule /ˈkaɪərəl/ is a type of molecule that lacks an internal plane of symmetry and thus has a non-superposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom
- One of the enantiomers is simply a non-superimposable mirror image of the other one. In other words, if one isomer looked in a mirror, what it would see is the other one. The two isomers (the original one and its mirror image) have a different spatial arrangement, and so can't be superimposed on each other. If an achiral molecule (one with a plane of symmetry) looked in a mirror, you would always find that by rotating the image in space, you could make the two look identical. It would be possible to superimpose the original molecule and its mirror image. Definición (Wikipedia): A chiral molecule /ˈkaɪərəl/ is a type of molecule that lacks an internal plane of symmetry and thus has a non-superposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom
- The asymmetric carbon atom in a compound (the one with four different groups attached) is often shown by a star. It's extremely important to draw the isomers correctly. Draw one of them using standard bond notation to show the 3-dimensional arrangement around the asymmetric carbon atom. Then draw the mirror to show the examiner that you know what you are doing, and then the mirror image.
- The asymmetric carbon atom in a compound (the one with four different groups attached) is often shown by a star. It's extremely important to draw the isomers correctly. Draw one of them using standard bond notation to show the 3-dimensional arrangement around the asymmetric carbon atom. Then draw the mirror to show the examiner that you know what you are doing, and then the mirror image.
- The asymmetric carbon atom in a compound (the one with four different groups attached) is often shown by a star. It's extremely important to draw the isomers correctly. Draw one of them using standard bond notation to show the 3-dimensional arrangement around the asymmetric carbon atom. Then draw the mirror to show the examiner that you know what you are doing, and then the mirror image.
- Reglas de prioridad 1. The higher the atomic number of the immediate substituent atom, the higher the priority. For example, H– < C– < N– < O– < Cl–. (Different isotopes of the same element are assigned a priority according to their atomic mass.) 2. If two substituents have the same immediate substituent atom, evaluate atoms progressively further away from the chiral center until a difference is found. For example, CH3– < C2H5– < ClCH2– < BrCH2– < CH3O–. 3. If double or triple bonded groups are encountered as substituents, they are treated as an equivalent set of single-bonded atoms. For example, C2H5– < CH2=CH– < HC≡C– By configuration: R- and S- For chemists, the R / S system is the most important nomenclature system for denoting enantiomers, which does not involve a reference molecule such as glyceraldehyde. It labels each chiral center R or S according to a system by which its substituents are each assigned a priority, according to the Cahn–Ingold–Prelog priority rules (CIP), based on atomic number. If the center is oriented so that the lowest-priority of the four is pointed away from a viewer, the viewer will then see two possibilities: If the priority of the remaining three substituents decreases in clockwise direction, it is labeled R (for Rectus, Latin for right), if it decreases in counterclockwise direction, it is S (for Sinister, Latin for left). This system labels each chiral center in a molecule (and also has an extension to chiral molecules not involving chiral centers). Thus, it has greater generality than the d/l system, and can label, for example, an (R,R) isomer versus an (R,S) — diastereomers. The R / S system has no fixed relation to the (+)/(−) system. An R isomer can be either dextrorotatory or levorotatory, depending on its exact substituents. The R / S system also has no fixed relation to the d/l system. For example, the side-chain one of serine contains a hydroxyl group, -OH. If a thiol group, -SH, were swapped in for it, the d/l labeling would, by its definition, not be affected by the substitution. But this substitution would invert the molecule's R / S labeling, because the CIP priority of CH2OH is lower than that for CO2H but the CIP priority of CH2SH is higher than that for CO2H. For this reason, the d/l system remains in common use in certain areas of biochemistry, such as amino acid and carbohydrate chemistry, because it is convenient to have the same chiral label for all of the commonly occurring structures of a given type of structure in higher organisms. In the d/l system, they are nearly all consistent - naturally occurring amino acids are all l, while naturally occurring carbohydrates are nearly all d. In the R / S system, they are mostly S, but there are some common exceptions. [edit] By optical activity: (+)- and (−)- An enantiomer can be named by the direction in which it rotates the plane of polarized light. If it rotates the light clockwise (as seen by a viewer towards whom the light is traveling), that enantiomer is labeled (+). Its mirror-image is labeled (−). The (+) and (−) isomers have also been termed d- and l-, respectively (for dextrorotatory and levorotatory). Naming with d- and l- is easy to confuse with d- and l- labeling and is therefore strongly discouraged by IUPAC.[10] [edit] By configuration: d- and l- An optical isomer can be named by the spatial configuration of its atoms. The d/l system does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself, and its two isomers are labeled d and l (typically typeset in small caps in published work). Certain chemical manipulations can be performed on glyceraldehyde without affecting its configuration, and its historical use for this purpose (possibly combined with its convenience as one of the smallest commonly used chiral molecules) has resulted in its use for nomenclature. In this system, compounds are named by analogy to glyceraldehyde, which, in general, produces unambiguous designations, but is easiest to see in the small biomolecules similar to glyceraldehyde. One example is the amino acid alanine, which has two optical isomers, and they are labeled according to which isomer of glyceraldehyde they come from. On the other hand, glycine, the amino acid derived from glyceraldehyde, has no optical activity, as it is not chiral (achiral). Alanine, however, is chiral. The d/l labeling is unrelated to (+)/(−); it does not indicate which enantiomer is dextrorotatory and which is levorotatory. Rather, it says that the compound's stereochemistry is related to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde—the dextrorotatory isomer of glyceraldehyde is, in fact, the d- isomer. Nine of the nineteen l-amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and d-fructose is also referred to as levulose because it is levorotatory. A rule of thumb for determining the d/l isomeric form of an amino acid is the "CORN" rule. The groups: COOH, R, NH2 and H (where R is a variant carbon chain) are arranged around the chiral center carbon atom. Starting with the hydrogen atom away from the viewer, if these groups are arranged clockwise around the carbon atom, then it is the d-form. If counter-clockwise, it is the l-form.
- Buena página para distinguir nomenclatura D- / L- de R- / S-: http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/sterism3.htm
- Buena página para distinguir nomenclatura D- / L- de R- / S-: http://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/sterism3.htm