Overview of Chapter Chapter 4 -...

Chapter 4

Alcohols & Halides

Functions, Nomenclature,Physical Properties &Chemical Reactions

(1) alcohol + hydrogen halide(1) alcohol + hydrogen halide

ROH + HX ROH + HX →→ RX + H RX + H22OO

(2) alkane + halogen(2) alkane + halogen

RH + XRH + X22 →→ RX + HX RX + HX

Both are substitution reactions.Both are substitution reactions.

Overview of ChapterOverview of Chapter

This chapter introduces 2 chemical reactions and This chapter introduces 2 chemical reactions and their mechanisms by focusing on two reactionstheir mechanisms by focusing on two reactionsthat yield alkyl halides.that yield alkyl halides.

4.24.2

IUPAC NomenclatureIUPAC Nomenclature

of Alkyl Halidesof Alkyl Halides

The two that are most widely used are:The two that are most widely used are:functional class nomenclaturefunctional class nomenclaturesubstituent substituent nomenclaturenomenclature

Both types can be applied to alcohols andBoth types can be applied to alcohols andalkyl halides.alkyl halides.


There are several kinds of IUPAC nomenclature.There are several kinds of IUPAC nomenclature.

Name the alkyl group and the halogen asName the alkyl group and the halogen asseparate words (separate words (alkylalkyl + + halidehalide).).

Functional Class Nomenclature of Alkyl HalidesFunctional Class Nomenclature of Alkyl Halides

CHCH33FF CHCH33CHCH22CHCH22CHCH22CHCH22ClCl

CHCH33CHCH22CHCHCHCH22CHCH22CHCH33

BrBr

HH

II

Name the alkyl group and the halogen asName the alkyl group and the halogen asseparate words (separate words (alkylalkyl + + halidehalide).).

Functional Class Nomenclature of Alkyl HalidesFunctional Class Nomenclature of Alkyl Halides

CHCH33FF CHCH33CHCH22CHCH22CHCH22CHCH22ClCl

CHCH33CHCH22CHCHCHCH22CHCH22CHCH33

BrBr

Methyl fluorideMethyl fluoride Pentyl chloridePentyl chloride

1-1-Ethylbutyl Ethylbutyl bromidebromide Cyclohexyl iodideCyclohexyl iodide

HH

II

Name as halo-substituted alkanes.Name as halo-substituted alkanes.

Number the longest chain containing theNumber the longest chain containing thehalogen in the direction that gives the lowesthalogen in the direction that gives the lowestnumber to the substituted carbon.number to the substituted carbon.

SubstituentSubstituent Nomenclature of Alkyl Halides Nomenclature of Alkyl Halides

CHCH33CHCH22CHCH22CHCH22CHCH22FF CHCH33CHCHCHCH22CHCH22CHCH33

BrBr

CHCH33CHCH22CHCHCHCH22CHCH33

II

Name as halo-substituted alkanes.Name as halo-substituted alkanes.

Number the longest chain containing theNumber the longest chain containing thehalogen in the direction that gives the lowesthalogen in the direction that gives the lowestnumber to the substituted carbon.number to the substituted carbon.

Substitutive Nomenclature of Alkyl HalidesSubstitutive Nomenclature of Alkyl Halides

CHCH33CHCH22CHCH22CHCH22CHCH22FF CHCH33CHCHCHCH22CHCH22CHCH33

BrBr1-Fluoropentane1-Fluoropentane

3-Iodopentane3-Iodopentane

2-Bromopentane2-BromopentaneCHCH33CHCH22CHCHCHCH22CHCH33

II


Halogen and alkyl groupsHalogen and alkyl groupsare of equal rank when are of equal rank when it comes to numberingit comes to numberingthe chain.the chain.

Number the chain in theNumber the chain in thedirection that gives the direction that gives the lowest number to thelowest number to thegroup (halogen or alkyl)group (halogen or alkyl)that appears first.that appears first.

CHCH33

ClCl

ClCl

CHCH33


5-Chloro-2-methylheptane5-Chloro-2-methylheptane

2-Chloro-5-methylheptane2-Chloro-5-methylheptane

CHCH33

ClCl

ClCl

CHCH33

4.34.3


of Alcoholsof Alcohols

Question 1• Name the compound on the right according

to the IUPAC system.

• A) 4-bromo-5-ethyl-2-methylheptane

• B) 4-bromo-3-ethyl-6-methylheptane

• C) 4-bromo-5-diethyl-2-methylpentane

• D) 4-bromo-3-ethyl-6-dimethylhexane

Name the alkyl group and add "alcohol" as aName the alkyl group and add "alcohol" as aseparate word.separate word.

Functional Class Nomenclature of AlcoholsFunctional Class Nomenclature of Alcohols

CHCH33CHCH22OHOH

CHCH33CHCHCHCH22CHCH22CHCH22CHCH33

OHOH

CHCH33CCHCCH22CHCH22CHCH33

OHOH

CHCH33

Name the alkyl group and add "alcohol" as aName the alkyl group and add "alcohol" as aseparate word.separate word.

Functional Class Nomenclature of AlcoholsFunctional Class Nomenclature of Alcohols

CHCH33CHCH22OHOH


OHOH


OHOH

CHCH33

Ethyl alcoholEthyl alcohol

1-Methylpentyl alcohol1-Methylpentyl alcohol

1,1-Dimethylbutyl1,1-Dimethylbutylalcoholalcohol

Name as "alkanols." Replace Name as "alkanols." Replace -e-e ending of alkane ending of alkanename with name with -ol-ol..

Number chain in direction that gives lowest numberNumber chain in direction that gives lowest numberto the carbon that bears the to the carbon that bears the ——OH group.OH group.

Substitutive Nomenclature of AlcoholsSubstitutive Nomenclature of Alcohols

CHCH33CHCH22OHOH


OHOH


OHOH

CHCH33

Name as "alkanols." Replace Name as "alkanols." Replace -e-e ending of alkane ending of alkanename with name with -ol-ol..

Number chain in direction that gives lowest numberNumber chain in direction that gives lowest numberto the carbon that bears the to the carbon that bears the ——OH group.OH group.


CHCH33CHCH22OHOH


OHOH


OHOH

CHCH33

EthanolEthanol

2-Hexanol or Hexan-2-ol2-Hexanol or Hexan-2-ol

2-Methyl-2-pentanol2-Methyl-2-pentanolor 2-Methylpentan-2-olor 2-Methylpentan-2-ol

OHOH

CHCH33


Hydroxyl groups outrank Hydroxyl groups outrank alkyl groups when alkyl groups when it comes to numberingit comes to numberingthe chain.the chain.

Number the chain in theNumber the chain in thedirection that gives the direction that gives the lowest number to thelowest number to thecarbon that bears thecarbon that bears theOH groupOH group

CHCH33

OHOH


6-Methyl-3-heptanol6-Methyl-3-heptanol

5-Methyl-2-heptanol5-Methyl-2-heptanol

OHOH

CHCH33

CHCH33

OHOH

Question 2• Name the compound on the right

according to the IUPAC system.

• A) 3,4-dimethyl-2-hydroxypentane

• B) 2,3-dimethyl-4-pentanol

• C) 3,4-dimethyl-2-pentanol

• D) 2,3-dimethylpentyl-2-alcohol

Question 3• Name the compound on the right

according to the IUPAC system.

• A) trans-2-methylhydroxypentanol

• B) trans-2-methylcyclopentanol

• C) cis-2-methylhydroxypentanol

• D) cis-2-methylcyclopentanol

4.44.4

Classes of AlcoholsClasses of Alcohols

and Alkyl Halidesand Alkyl Halides

Alcohols and alkyl halides are classified asAlcohols and alkyl halides are classified asprimaryprimarysecondarysecondarytertiarytertiary

according to their "degree of substitution."according to their "degree of substitution."

Degree of substitution is determined by countingDegree of substitution is determined by countingthe number of carbon atoms directly attached tothe number of carbon atoms directly attached tothe carbon that bears the halogen or hydroxyl group.the carbon that bears the halogen or hydroxyl group.

ClassificationClassification

Different Kinds of Alkyl Halides

CHCH33CHCH22CHCH22CHCH22CCHH22FF

CHCH33CCHCHHCH22CHCH22CHCH33

BrBr

primary alkyl halideprimary alkyl halide

secondary alkyl halidesecondary alkyl halide

ClassificationClassification

CHCH33CCCHCH22CHCH22CHCH33

OHOH

CHCH33

tertiary alcoholtertiary alcohol

HH

OHOH

secondary alcoholsecondary alcohol

Question 4

• What type of alcohol is 2-methyl-3-pentanol?

• A) primary (1°)

• B) secondary (2°)

• C) tertiary (3°)

• D) quaternary (4°)

4.5Bonding in Alcohols

and Alkyl Halides

Structures of Alkyl Halides

HH

HH

HH

•alcohols and alkyl halides are polar

µµ = 1.7 D = 1.7 D µµ = 1.9 D = 1.9 D

HH

HH

CC OO

HH

HH

CC ClClδδ++

δδ––δδ––δδ++

δδ++

Dipole Moments

•alcohols and alkyl halides are polar

µµ = 1.7 D = 1.7 D µµ = 1.9 D = 1.9 D

Dipole Moments

•Boiling point•Solubility in water

•Density

4.6Physical Properties of

Alcohols and Alkyl Halides:Intermolecular Forces

• 44 48 46

• -42 -32 +78

• 0 1.9 1.7

CHCH33CHCH22CHCH33 CHCH33CHCH22FF CHCH33CHCH22OHOH

MolecularMolecularweightweight

BoilingBoilingpoint, point, °°CC

DipoleDipolemoment, Dmoment, D

Effect of Structure on BoilingPoint

• 44

• -42

• 0

CHCH33CHCH22CHCH33




Intermolecular forcesIntermolecular forcesare weak.are weak.

Only intermolecularOnly intermolecularforces are inducedforces are induceddipole-induced dipoledipole-induced dipoleattractions.attractions.


• 48

• -32

• 1.9

CHCH33CHCH22FF




A polar molecule;A polar molecule;therefore dipole-dipoletherefore dipole-dipoleand dipole-inducedand dipole-induceddipole forces contributedipole forces contributeto intermolecular to intermolecular attractions.attractions.


• 46

• +78

• 1.7

CHCH33CHCH22OHOH




Highest boiling point;Highest boiling point;strongest intermolecularstrongest intermolecularattractive forces.attractive forces.

Hydrogen bonding isHydrogen bonding isstronger than otherstronger than otherdipole-dipole attractions.dipole-dipole attractions.


δδ++δδ––

δδ––δδ++

Hydrogen bonding in ethanol Hydrogen bonding in ethanol

Boiling point increases with numberof halogens

• CH3Cl -24°C• CH2Cl2 40°C• CHCl3 61°C• CCl4 77°C

CompoundCompound Boiling PointBoiling Point

Even though CClEven though CCl4 4 is the only compound in this list withoutis the only compound in this list withouta dipole moment, it has the highest boiling point.a dipole moment, it has the highest boiling point.

Induced dipole-induced dipole forces are greatest in CClInduced dipole-induced dipole forces are greatest in CCl44because it has the greatest number of Cl atoms. Cl is morebecause it has the greatest number of Cl atoms. Cl is morepolarizablepolarizable than H. (NOTE:Fluorine does not follow the than H. (NOTE:Fluorine does not follow thepattern.)pattern.)

Solubility in water

•Alkyl halides are insoluble in water.

•Methanol, ethanol, isopropyl alcohol arecompletely miscible with water.

•The solubility of an alcohol in waterdecreases with increasing number of carbons (compound becomesmore hydrocarbon-like).

δδ++δδ––

δδ––

δδ++

δδ––δδ++

Hydrogen Bonding BetweenEthanol and Water Density

•Alkyl fluorides and alkyl chlorides areless dense than water.

•Alkyl bromides and alkyl iodides are more dense than water.

•All liquid alcohols have densities of about 0.8 g/mL.

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