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Alkenes Structure,

Nomenclature, and

an introduction toReactivity •

Thermodynamics

and Kinetics

Paula Yurkanis Bruice

University of alifornia,

Santa Bar!ara

Chapter 4

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Alkenes

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Saturated and

Unsaturated !drocar"ons

Saturated h!drocar"ons ha#e no dou"le "onds.

Unsaturated h!drocar"ons ha#e one or $ore dou"le "onds.

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%o$enclature o& Alkenes

'eplace (ane) o& alkane *ith (ene.)

+he &unctional roup ets the lo*est possi"le nu$"er.

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Stereoiso$ers o& an Alkene are na$ed

usin a cis or trans Pre&i-

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%o$enclature o& ienes

t*o dou"le "onds / diene

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%u$"er in the direction so that the &unctional roup ets the

lo*est nu$"er.


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Su"stituents are stated in alpha"etical order .


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%o$enclature o& C!clic Alkenes

A nu$"er is not needed to denote the position o& the

&unctional roup it is al*a!s "et*een C1 and C2.

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in!lic and All!lic Car"ons

#in!lic car"on the sp2 car"on o& an alkene

all!lic car"on a car"on ad3acent to a #in!lic car"on

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'eactions o& ranic Co$pounds

ranic co$pounds can "e di#ided into &a$ilies.

All $e$"ers o& a &a$il! react in the sa$e *a!. +he &a$il! a

co$pound "elons to depends on its &unctional roup.

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Each &a$il! can "e put in one

o& &our 5roups

+he &a$ilies in a roup react in si$ilar *a!s.

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Electrophiles

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%ucleophiles

A nucleophile hasa neati#e chare

a lone pair

a dou"le "ond

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A %ucleophile reacts

*ith an Electrophile

our &irst oranic reaction is a t*o7step reaction.

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Cur#ed Arro*s

+he $echanis$ o& a reaction is the step7"!7step description o&

the process "! *hich reactants are con#erted into products.

&irst step o& the reaction

Cur#ed arro*s are used to sho* the $echanis$ o& a reaction.

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second step o& the reaction

+he cur#ed arro* sho*s *here the electrons start &ro$

and *here the! end up.

Cur#ed Arro*s

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o* to dra* Cur#ed Arro*s

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A 'eaction Coordinate iara$

A reaction

coordinate diara$

sho*s the ener!

chanes that take

place in each step

o& a reaction.

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+her$od!na$ics and 8inetics

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+he E9uili"riu$ Constant

+he e9uili"riu$ constant i#es the concentration o& reactants

and products at e9uili"riu$.

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E-eronic and Enderonic 'eactions

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5i""s :ree7Ener! Chane ;<G=>

?G= / &ree ener! o& the products @&ree ener! o& the reactants

?H = / heat re9uired to "reak "ones @

heat released &ro$ &or$in "onds

?S= / &reedo$ o& $otion o& the products @

&reedo$ o& $otion o& the reactants

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A 'eduction 'eaction

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Catal!tic !droenation

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Usin <H = alues to deter$ine

the 'elati#e Sta"ilities o& Alkenes

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Usin <H = alues to deter$ine

the 'elati#e Sta"ilities o& Alkenes

+he relati#e eneries ;sta"ilities> o& three alkenes that can "e catal!ticall!

h!droenated to 27$eth!l"utane. +he $ost sta"le alkene has the s$allest heat o&

h!droenation. ;%otice that *hen a reaction coordinate diara$ sho*s <H = #alues,

the y 7a-is is potential ener! *hen it sho*s <G= #alues, the y 7a-is is &ree ener!

:iure B.2.>

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'elati#e Sta"ilities o& Alkenes

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'elati#e Sta"ilities o&

Cis and +rans Alkenes

' l ti St "iliti &

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'elati#e Sta"ilities o&

ialk!l7Su"stituted Alkenes

8i ti & t i th

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8inetics o* &ast is the

product &or$edD

<G / &ree ener! o& the transition state 7 &ree ener! o& the reactants

+he reater the ener! "arrier, the slo*er the reaction.

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'ate o& a 'eaction

Increasin the concentration increases the rate.

Increasin the te$perature increases the rate.

+he rate can also "e increased "! a catal!st.

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An Electrophilic Addition 'eaction

+ransition states ha#e partiall! &or$ed "onds.

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'eaction Coordinate iara$ &or each step

o& the addition o& Fr to 27Futene

C &

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'eaction Coordinate iara$ &or

the addition o& Fr to 27Futene

+he rate7li$itin

step o& the

reaction is the

step that has itstransition state at

the hihest point

o& the reaction

coordinate

diara$.

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A Catal!st

A catal!st pro#ides a path*a! &or a reaction *ith a lo*er

ener! "arrier.

A catal!st does not chane the ener! o& the startin point

;the reactants> or the ener! o& the end point ;the products>.

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EnG!$es

Host "ioloical reactions re9uire a catal!st.

Host "ioloical catal!sts are proteins called enG!$es.

+he reactant o& a "ioloical reaction is called a su"strate.

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+he Acti#e Site o& an EnG!$e

An enG!$e "inds its su"strate at its acti#e site.

E Sid Ch i th t

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EnG!$e Side Chains that

"ind the Su"strate

So$e enG!$e side chains "ind the su"strate.

So$e enG!$e side chains are acids, "ases, and nucleophiles

that catal!Ge the reaction.


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So$e enG!$e side chains are acids, "ases, and nucleophiles

that catal!Ge the reaction.


catal!Ge the 'eaction

04 lecture

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