01:160:307 Lecture Notes - Lecture 6: Electrophilic Addition, Stereospecificity, Hydrogenation
1 May 2018
School
Department
Course
Professor
OC 307 – Chapter 06 – Alkene Reactions – H. D. Roth
1
Chapter 06 – Alkene Reactions – ctd.
Reactions
For the catalytic hydrogenation we have discussed the stereochemistry of addition. For the many
remaining reactions of alkenes we will discuss these features:
Regiochemistry & Stereochemistry
as well as Selectivity & Specificity
The term stereochemistry relates whether two groups are added to the two carbons randomly or
whether they are added in a specific way, i.e., from the same side (stereospecific syn, cis) or from
opposite sides (stereospecific anti. trans).
The term regiochemistry relates whether two alkene carbons, that are differently substituted, react
at the same rate (two products formed in comparable yields, regiorandom reaction), or whether
one carbon reacts preferentially (one major product formed, regioselective) or exclusively (only
one product is formed, regiospecific).
!"#$%&'()*"*$+,--*%*'./+
+
,+0#1*/+,$*-+*/+2.+#"#$%&'.+(2*&+2$$#(%'&3+*%+*/+2.+#"#$%&'()*"#4+++
,+0#1*/+52/#+*/+2.+#"#$%&'.+(2*&+-'.'&3+*%+*/+2+.6$"#'()*"#4+++
,"7#.#/3+)28*.9+%1'+p+#"#$%&'./3+2&#+0#1*/+52/#/3+#"#$%&'.+(2*&+-'.'&/3+.6$"#'()*"#/+:+%)#;+
$%+1*%)+#"#$%&'()*"#/3+)#.$#+#"#$%&'()*"*$+2--*%*'.4++
24++++<#.#&2"+='./*-#&2%*'./+
2>4+?#9*'$)#@*/%&;+
,"7#.#/+@2;+$%+1*%)+2+#.%+A:B+C;+("2$*.9+/6C/%*%6#.%+A+2%+2+/(#$*D*$+$2&C'.+'&+
&2.-'@";+2%+#*%)#&+$2&C'.4++
OC 307 – Chapter 06 – Alkene Reactions – H. D. Roth
2
+ + +
ED+%)#+$%*'.+'$$6&/+2%+2+/(#$*D*$+$2&C'.3+*%+*/+$2""#-+	*'/(#$*D*$F+2+&2.-'@+$%*'.+*/+
	*'&2.-'@4+
2G4+H%#&#'$)#@*/%&;+
I)#&#+2&#+%)&##+('//*C"#+/%#&*$+'6%$'@#/+D'&+/6C/%*%6#.%/+A+2.-+B+2--#-+%'+2.+2"7#.#/J++
*K+%)#;+@2;+#.-+6(+'.+%)#+/2@#+D2$#+'D+%)#+2"7#.#+L$*/M3+/;.MKF++
**K+%)#;+@2;+#.-+6(+'.+'(('/*%#+D2$#/+'D+%)#+2"7#.#+L%&2./M3+2.%*MKF+
***K+I)#;+@2;+#.-+6(+&2.-'@";4+
+ +
+
ED+%)#+/6C/%*%6#.%/+#.-+6(+'.+%)#+/2@#+D2$#+1#+$2""+%)#+$%*'.+/%#&#'/(#$*D*$+$*/+L'&+/;.KF+*D+
%)#+/6C/%*%6#.%/+#.-+6(+'.+'(('/*%#+D2$#/+1#+$2""+%)#+$%*'.+/%#&#'/(#$*D*$+%&2./+L'&+2.%*KF+
*D+%)#+/6C/%*%6#.%/+#.-+6(+&2.-'@";+1#+$2""+%)#+$%*'.+/%#&#'&2.-'@4+
ED+2+$)*&2"+$#.%#&/+*/+$%#-3+1#+.##-+%'+-#%#&@*.#+1)#%)#&++
+ *K+2+/*.9"#+#.2.%*'@#&+*/+D'&@#-3++
+**K+2+(2*&+'D+#.2.%*'@#&/+*/+D'&@#-+L2+&2$#@2%#K3++
+***K+2+@#/'+$'@('6.-+*/+D'&@#-3+'&+
+*8K+2+@*N%6&#+'D+/%#&#'*/'@#&/+*/+D'&@#-4+
+
OP++=":+++L5&:K++++);-&')2"'9#.2%*'.+
OP++QO:+++++);-&2%*'.+
5&P++5&:++ + + + C&'@*.2%*'.+
5&P++QO:++ + + + )2"');-&*.#+D'&@2%*'.+
O9PQ,$+++Q,$:++ + + 'N*@#&$6&2%*'.+LR&#-6$%*'.K+
5OS+++L5POG++O:K++++);-&'C'&2%*'.+LR'N*-2%*'.K+
TQU++++++++(#&2$*-+'N*-2%*'.+
QS++++++++'V'.'";/*/+L=W=+$"#2829#K+
Q/QX++++++++-*);-&'N;"2%*'.+L'N*-2%*'.K+
+
C C
H
H
R
R
C C
H
H
R
R
X
+
C C
H
H
R
R
C C
H
H
R
R
X
CC
R
R
H
H
X
++
C C
H
H
R
R
XY
C C
H
H
R
R
C C
H
H
R
R
X
Y
C C
H
H
R
R
XY
OC 307 – Chapter 06 – Alkene Reactions – H. D. Roth
3
+++++!"#$%&'()*"*$+?#29#.%/+$2.+
+++ +C'.-+%'+>+=++++'&++++C'.-+%'+G+=+
'D+%)#+2"7#.#+
D'&@*.9+*.%#&@#-*2%#/+'D+-*DD#&#.%+/%&6$%6&#+%;(#/+
+
++++>M=++$%*'./+D'&@++++++++GM=++$%*'./+D'&@+
+++++++++++$2&C'$2%*'./+ + + + '.*6@+/(#$*#/+'&+.#6%&2"+2--6$%/+
O;-&')2"'9#.2%*'.+
++++++
+ +
+
+
L.'%+'C/#&8#-K+ +
H6@@2&;+>J+<#.#&2"+$)2.9#/J+I)# p+C'.-+*/+C&'7#.F+%)#+O:5&+s+C'.-+*/+C&'7#.F+2+.#1+=MO+s+
C'.-+*/+@2-#F+2.-+2+.#1+=M5&+s+C'.-+*/+@2-#++ +
H6@@2&;+GJ+Y#&%2*.*.9+%'+	*'$)#@*/%&;J+I)#+="+'&+5&+/##@/+%'+#.-+6(+'.+%)#+@'&#+)*9)";+
/6C/%*%6%#-+$2&C'.4++
O'1+-'+1#+&2%*'.2"*V#+1)#&#+%)#+(&'%'.+*/+2%%2$)#-+%'+2.+6./;@@#%&*$+2"7#.#Z+ [#+$2.+
6/#++ + >K+#@(*&*$2"+$&*%#&*2+'&++
++++++++GK+'6&+%)#'&#%*$2"+6.-#&/%2.-*.94++
\2&7'8.*7'8+:+!@(*&*$2"+,((&'2$)+
+
+
[4+\2&7'8.*7'83+>]^_3+
6/#-+#@(*&*$2"+$&*%#&*2+L'6%$'@#+'D+$%*'./K+%'+
D'&@6"2%#+%)*/+?`0!J+%)#+O+'D+O:A+*/+2--#-+%'+%)#+$2&C'.+
%)2%+)2/+@'&#+O4+
%)2%+@#2./+%)2%+A+*/+2--#-+%'+%)#+@'&#+)*9)";+/6C/%*%6%#-+
$2&C'.4++
[#+$2""+%)*/+%;(#+'D+$%*'.+2+\2&7'8.*7'8+2--*%*'.4+
B'6+/)'6"-+understand+\2&7'8.*7'8a/+?`0!+2/+D'""'1/J++
9*8#.+%)2%+2.+2"7#.#+*/+2+0#1*/+C2/#+2.-+%)2%+O:5&+*/+2.+
2$*-3+*%+*/+"*7#";+%)2%+2+(&'%'.+LOPK+*/+2--#-+%'+%)#+2"7#.#3+
9#.#&2%*.9+2+$2&C'$2%*'.4+
\2&7'8.*7'8a/+?`0!+%)#.+@#2./+%)2%+%)#+O+'D+O:A+*/+
2--#-+%'+2.+2"7#.#+/'+2/+%'+@27#+%)#+more+stable+
$2&C'$2%*'.4+
CH3CCH2Br
CH3
H
Document Summary
For the catalytic hydrogenation we have discussed the stereochemistry of addition. For the many remaining reactions of alkenes we will discuss these features: The term stereochemistry relates whether two groups are added to the two carbons randomly or whether they are added in a specific way, i. e. , from the same side (stereospecific syn, cis) or from opposite sides (stereospecific anti. trans). A lewis acid is an electron pair acceptor, it is an electrophile. A lewis base is an electron pair donor, it is a nucleophile. Alkenes, having two p electrons, are lewis bases, electron pair donors, nucleophiles they react with electrophiles, hence electrophilic addition: general considerations a1. Alkenes may react with a reagent x y by placing substituent x at a specific carbon or randomly at either carbon. If the reaction occurs at a specific carbon, it is called regiospecific; a random reaction is regiorandom. a2.
