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Chapter 10. Alkyl Halides. Alkyl Halides. Naming Synthesis - from alkene, alkane, & alcohol Reactions - Organometallic. Naming. 1,3-Dichloro-3-methylbutane. Naming. *. *. 2-Bromo-5-chlorohexane. (R or S)-2-Bromo-(R or S )-5-chlorohexane ( if 3-dimension structure is given ). Naming.

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Chapter 10

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Chapter 10

Alkyl Halides

Chapter 10 - Alkyl Halides


Alkyl Halides

  • Naming

  • Synthesis - from alkene, alkane, & alcohol

  • Reactions - Organometallic

Chapter 10 - Alkyl Halides


Naming

1,3-Dichloro-3-methylbutane

Chapter 10 - Alkyl Halides


Naming

*

*

2-Bromo-5-chlorohexane

(R or S)-2-Bromo-(R or S )-5-chlorohexane

(if 3-dimension structure is given)

Chapter 10 - Alkyl Halides


Naming

*

*

*

4-sec-Butyl-2-chlorononane

Chapter 10 - Alkyl Halides


Naming

1,1-Dibromo-4-tert-butylcyclohexane

Chapter 10 - Alkyl Halides


Naming

*

5-Iodo-2-hexene

Chapter 10 - Alkyl Halides


Naming

1-Bromo-6-chloro-2-hexyne

Chapter 10 - Alkyl Halides


Naming

*

*

cis-1-Bromo-2-ethylcyclopentane

cis-(R)-1-Bromo-(S)-2-ethylcyclopentane

Chapter 10 - Alkyl Halides


Alkyl Halides

  • Naming

  • Synthesis - from alkene, alkane, & alcohol

  • Reactions - Organometallic

Chapter 10 - Alkyl Halides


Synthesis

  • Alkene + HX(X=Cl, Br, or I) or X2 (X=Cl or Br )

  • Radical Halogenation of Alkanes

  • Allylic Halogenation of Alkenes

  • From Alcohol

Chapter 10 - Alkyl Halides


M

HX

ether

X2

CH2Cl2

KMnO4, H3O+

X2

O3

H2O(xs)

Zn/H3O+

HgAc2, H2O/THF

CH2I2

NaBH4

Zn(Cu) ether

BH3, THF

CHCl3

H2O2, OH-

KOH

H2

OsO4

NaHSO4, H2O

Pd or Pt

halogenation

anti

halohydrination

oxidation

M

anti

oxymercuration

M

oxidation

Alkene

hydroboration

non-M

syn

Simmons-Smith

syn

hydrogenation

syn

carbenation

syn

syn

hydroxylation

Chapter 10 - Alkyl Halides


Synthesis

  • Alkene + HX(X=Cl, Br, or I) or X2 (X=Cl or Br )

  • Radical Halogenation of Alkanes

  • Allylic Halogenation of Alkenes

  • From Alcohol

Chapter 10 - Alkyl Halides


Radical Chlorination of Methane

h or heat

h or heat

h or heat

Chapter 10 - Alkyl Halides


h or

heat

Chlorination of alkanes

Monochloro-

Chiral, racemic

*

achiral

achiral

*

+ others...

chiral, racemic

*

chiral, racemic

achiral

Chapter 10 - Alkyl Halides


h or

heat

Chlorination of alkanes

Monochloro-

1o

3o

and others...

2o

2o

Yields are different,

with 3o > 2o > 1o

(see p. 361)

1o

Chapter 10 - Alkyl Halides


relative

reactivity(rr)

expected

yield

#H  rr

# H

6

1.0

6.0

21%

1

5.0

5.0

18%

2

3.5

7.0

25%

2

3.5

7.0

25%

3

1.0

3.0

11%

 = 28.0

see p. 361

Chapter 10 - Alkyl Halides


Reactivity

Stability

Radical Chlorination of Alkane

Yields 3o > 2o > 1o implies that ...

Hammond

Postulate

Chapter 10 - Alkyl Halides


Synthesis

  • Alkene + HX(X=Cl, Br, or I) or X2 (X=Cl or Br )

  • Radical Halogenation of Alkanes

  • Allylic Halogenation of Alkenes

  • From Alcohol

Chapter 10 - Alkyl Halides


allylic

361 kJ/mol

Vinylic C—H

444 kJ/mol

alkyl

401 kJ/mol

Allylic

p 172, Table 5.3

1. Radical reactions take place at the allylic position.

2. Allylic hydrogen is more acidic than alkyl and vinylic hydrogen.

Chapter 10 - Alkyl Halides


vinylic

allylic

1o

2o

3o

Radical Chlorination of Alkane

Stability

Chapter 10 - Alkyl Halides


allylic

vinylic

Allylic vs. vinylic Stability

Resonance

more stable

No resonance

less stable

Chapter 10 - Alkyl Halides


Allylic

position

Allylic

position

p 237

trans-2-Bromo-1-cyclohexynol

*

p 364

3-Bromocyclohexene

*

*

Chapter 10 - Alkyl Halides


Synthesis

  • Alkene + HX(X=Cl, Br, or I) or X2 (X=Cl or Br )

  • Radical Halogenation of Alkanes

  • Allylic Halogenationof Alkenes

  • From Alcohol

Chapter 10 - Alkyl Halides


Alcohol  Alkyl Halides

ROH + HX  RX + H2O

Chapter 10 - Alkyl Halides


ROH + HX  RX + H2O

Ethers, carbonyl,

and aromatic rings

do not interfere.

High yield

Chapter 10 - Alkyl Halides


Synthesis

  • Alkene + HX(X=Cl, Br, or I) or X2 (X=Cl or Br )

  • Radical Halogenation of Alkanes

  • Allylic Halogenation of Alkenes

  • From Alcohol

Chapter 10 - Alkyl Halides


Alkyl Halides

  • Naming

  • Synthesis - from alkene, alkane, & alcohol

  • Reactions - Organometallic

Chapter 10 - Alkyl Halides


ether

R — X + Mg R — Mg — X

or THF

Organometallic Reactions

Organomagnesium halides, RMgX, - Grignard Reagents.

R = 1o, 2o, 3o, alkyl, alkenyl (vinyl), or aryl.

X = Cl, Br, or I

Chapter 10 - Alkyl Halides


Organometallic Reactions

Organolithium reagent, RLi.

Chapter 10 - Alkyl Halides


Organometallic Compound

1. Although RMgX and Rli are polar covalent, they are still soluble in nonpolar pentane.

2. RMgX and RLi are strong bases.

Chapter 10 - Alkyl Halides


25

16-18

15.7

9-10

8-9

4-5

51

38-40

pKa:

pKa:

1. RMgX is a strong base.

2. CH3CH2MgBr will react with all the listed

compounds.

Chapter 10 - Alkyl Halides


Organometallic Reactions

Lengthen small molecules.

Chapter 10 - Alkyl Halides


Alkyl Halides

  • Naming

  • Synthesis - from alkene, alkane, & alcohol

  • Reactions - Organometallic

Chapter 10 - Alkyl Halides


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