2. Curso Básico de Química Orgánica
http://triplenlace.com/cbqo/
Este ejercicio pertenece al
3. Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
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Consejo
Trate de resolver este ejercicio (y todos) por sí
mismo/a antes de ver las soluciones. Si no lo intenta,
no lo asimilará bien.
4. CH2
CH
Br2
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
5. CH2
CH
Br2
-
+
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Existe una cierta
polaridad en el triple
enlace debido a la
asimetría de la
molécula
triplenlace.com
6. Br Br
+ -
Br2
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Y también existe una cierta polaridad en el enlace Br-Br debido al
desplazamiento periódico de la nube de carga del enlace. En el
transcurso de la reacción los dos electrones del enlace llegarán a
quedarse en uno de los Br formándose Br+ y :Br-
triplenlace.com
CH2
CH
-
+
Br+ + :Br-
7. Br2
CH2
Br
Br
3,4-dibromo-1,3-butadieno
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Se produce entonces un ataque
electrofílico del Br+ al triple enlace,
quedando unido este Br + a un C. El
otro resto del Br2 original, :Br-, se une
al C vecino utilizando sus dos
electrones para formar el enlace
correspondiente
triplenlace.com
CH2
CH
-
+
8. Br2
CH2
Br
Br
3,4-dibromo-1,3-butadieno
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
De este modo se ha producido la adición de la molécula de Br2 a la
molécula H2C=C-C≡CH y la conversión del triple enlace en doble
triplenlace.com
CH2
CH
-
+
9. Br2
CH2
Br
Br
3,4-dibromo-1,3-butadieno
Br2
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Como el Br2 está en
exceso seguirá
adicionándose
electrofílicamente…
triplenlace.com
CH2
CH
-
+
13. Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
Ahora vamos con la segunda parte del
ejercicio
14. Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Se trata de una adición catalítica al doble enlace.
Este es un ejemplo genérico:
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15. Hidrogenación catalítica (adición)
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Este es el mecanismo
triplenlace.com
16. Hidrogenación catalítica (adición)
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Este es el mecanismo
triplenlace.com
17. Hidrogenación catalítica (adición)
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Este es el mecanismo
triplenlace.com
18. Hidrogenación catalítica (adición)
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Este es el mecanismo
triplenlace.com
19. Hidrogenación catalítica (adición)
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Este es el mecanismo
triplenlace.com
20. Hidrogenación catalítica (adición)
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
Este es el mecanismo
triplenlace.com
21. H2
Pt
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
CH2
CH
22. H2
1,3-butadieno
Pt
CH2
CH2
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
CH2
CH
El H2 se adiciona al
triple enlace…
23. H2
Pt
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
Pero si se sigue
hidrogenando se
seguirá adicionado al
resto de las
insaturaciones
H2
1,3-butadieno
Pt
CH2
CH2
CH2
CH
24. H2
1-buteno
Pt
CH3
CH2
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
H2
1,3-butadieno
Pt
CH2
CH2
CH2
CH
25. H2
1-buteno
Pt
CH3
CH2
H2
Pt
Se hace reaccionar 1-butén-3-ino con Br2 en exceso. ¿Qué se obtiene? ¿Y si se trata
dicho compuesto con H2 en exceso en presencia de Pt?
triplenlace.com
H2
1,3-butadieno
Pt
CH2
CH2
CH2
CH
Addition of hydrogen to a carbon-carbon double bond is called hydrogenation. The overall effect of such an addition is the reductive removal of the double bond functional group. Regioselectivity is not an issue, since the same group (a hydrogen atom) is bonded to each of the double bond carbons. The simplest source of two hydrogen atoms is molecular hydrogen (H2), but mixing alkenes with hydrogen does not result in any discernible reaction. Although the overall hydrogenation reaction is exothermic, a high activation energy prevents it from taking place under normal conditions. This restriction may be circumvented by the use of a catalyst, as shown in the following diagram. Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product. Catalysts act by lowering the activation energy of reactions, but they do not change the relative potential energy of the reactants and products. Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts. Catalytic hydrogenation takes place in at least two stages, as depicted in the diagram. First, the alkene must be adsorbed on the surface of the catalyst along with some of the hydrogen. Next, two hydrogens shift from the metal surface to the carbons of the double bond, and the resulting saturated hydrocarbon, which is more weakly adsorbed, leaves the catalyst surface. The exact nature and timing of the last events is not well understood.
Addition of hydrogen to a carbon-carbon double bond is called hydrogenation. The overall effect of such an addition is the reductive removal of the double bond functional group. Regioselectivity is not an issue, since the same group (a hydrogen atom) is bonded to each of the double bond carbons. The simplest source of two hydrogen atoms is molecular hydrogen (H2), but mixing alkenes with hydrogen does not result in any discernible reaction. Although the overall hydrogenation reaction is exothermic, a high activation energy prevents it from taking place under normal conditions. This restriction may be circumvented by the use of a catalyst, as shown in the following diagram. Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product. Catalysts act by lowering the activation energy of reactions, but they do not change the relative potential energy of the reactants and products. Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts. Catalytic hydrogenation takes place in at least two stages, as depicted in the diagram. First, the alkene must be adsorbed on the surface of the catalyst along with some of the hydrogen. Next, two hydrogens shift from the metal surface to the carbons of the double bond, and the resulting saturated hydrocarbon, which is more weakly adsorbed, leaves the catalyst surface. The exact nature and timing of the last events is not well understood.
Addition of hydrogen to a carbon-carbon double bond is called hydrogenation. The overall effect of such an addition is the reductive removal of the double bond functional group. Regioselectivity is not an issue, since the same group (a hydrogen atom) is bonded to each of the double bond carbons. The simplest source of two hydrogen atoms is molecular hydrogen (H2), but mixing alkenes with hydrogen does not result in any discernible reaction. Although the overall hydrogenation reaction is exothermic, a high activation energy prevents it from taking place under normal conditions. This restriction may be circumvented by the use of a catalyst, as shown in the following diagram. Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product. Catalysts act by lowering the activation energy of reactions, but they do not change the relative potential energy of the reactants and products. Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts. Catalytic hydrogenation takes place in at least two stages, as depicted in the diagram. First, the alkene must be adsorbed on the surface of the catalyst along with some of the hydrogen. Next, two hydrogens shift from the metal surface to the carbons of the double bond, and the resulting saturated hydrocarbon, which is more weakly adsorbed, leaves the catalyst surface. The exact nature and timing of the last events is not well understood.
Addition of hydrogen to a carbon-carbon double bond is called hydrogenation. The overall effect of such an addition is the reductive removal of the double bond functional group. Regioselectivity is not an issue, since the same group (a hydrogen atom) is bonded to each of the double bond carbons. The simplest source of two hydrogen atoms is molecular hydrogen (H2), but mixing alkenes with hydrogen does not result in any discernible reaction. Although the overall hydrogenation reaction is exothermic, a high activation energy prevents it from taking place under normal conditions. This restriction may be circumvented by the use of a catalyst, as shown in the following diagram. Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product. Catalysts act by lowering the activation energy of reactions, but they do not change the relative potential energy of the reactants and products. Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts. Catalytic hydrogenation takes place in at least two stages, as depicted in the diagram. First, the alkene must be adsorbed on the surface of the catalyst along with some of the hydrogen. Next, two hydrogens shift from the metal surface to the carbons of the double bond, and the resulting saturated hydrocarbon, which is more weakly adsorbed, leaves the catalyst surface. The exact nature and timing of the last events is not well understood.
Addition of hydrogen to a carbon-carbon double bond is called hydrogenation. The overall effect of such an addition is the reductive removal of the double bond functional group. Regioselectivity is not an issue, since the same group (a hydrogen atom) is bonded to each of the double bond carbons. The simplest source of two hydrogen atoms is molecular hydrogen (H2), but mixing alkenes with hydrogen does not result in any discernible reaction. Although the overall hydrogenation reaction is exothermic, a high activation energy prevents it from taking place under normal conditions. This restriction may be circumvented by the use of a catalyst, as shown in the following diagram. Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product. Catalysts act by lowering the activation energy of reactions, but they do not change the relative potential energy of the reactants and products. Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts. Catalytic hydrogenation takes place in at least two stages, as depicted in the diagram. First, the alkene must be adsorbed on the surface of the catalyst along with some of the hydrogen. Next, two hydrogens shift from the metal surface to the carbons of the double bond, and the resulting saturated hydrocarbon, which is more weakly adsorbed, leaves the catalyst surface. The exact nature and timing of the last events is not well understood.
Addition of hydrogen to a carbon-carbon double bond is called hydrogenation. The overall effect of such an addition is the reductive removal of the double bond functional group. Regioselectivity is not an issue, since the same group (a hydrogen atom) is bonded to each of the double bond carbons. The simplest source of two hydrogen atoms is molecular hydrogen (H2), but mixing alkenes with hydrogen does not result in any discernible reaction. Although the overall hydrogenation reaction is exothermic, a high activation energy prevents it from taking place under normal conditions. This restriction may be circumvented by the use of a catalyst, as shown in the following diagram. Catalysts are substances that changes the rate (velocity) of a chemical reaction without being consumed or appearing as part of the product. Catalysts act by lowering the activation energy of reactions, but they do not change the relative potential energy of the reactants and products. Finely divided metals, such as platinum, palladium and nickel, are among the most widely used hydrogenation catalysts. Catalytic hydrogenation takes place in at least two stages, as depicted in the diagram. First, the alkene must be adsorbed on the surface of the catalyst along with some of the hydrogen. Next, two hydrogens shift from the metal surface to the carbons of the double bond, and the resulting saturated hydrocarbon, which is more weakly adsorbed, leaves the catalyst surface. The exact nature and timing of the last events is not well understood.
