Chapter 13 Alcohols, Ethers, Thiols

Organic and Biochem

Section 13.2 Structure

• Alcohols • Functional group: -OH (hydroxyl)

• Ethers • Functional group: -O-

• Thiols • Functional group: -SH (sulfhydryl)

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Section 13.2 Structure

• Alcohols • Functional group: -OH (hydroxyl)

• Ethers • Functional group: -O-

• Thiols • Functional group: -SH (sulfhydryl)

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Section 13.2 Structure

• Alcohols • Functional group: -OH (hydroxyl)

• Ethers • Functional group: -O-

• Thiols • Functional group: -SH (sulfhydryl)

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Section 13.3 Nomenclature

• Alcohols

• Select longest chain containing –OH

• Number chain from end closest to –OH

• Drop “e” of the parent chain and add “ol”

• Use a number to show the location of the –OH

• -OH takes precedence over alkyls & halogens

• Start numbering cyclic alcohols at C with –OH

• Common names come from the alkyl group bonded to the –OH

• Have “alcohol” in their common names

– Ethyl alcohol?

– Isopropyl alcohol?

– Isobutyl alcohol?

– Tertbutyl alcohol?

CH3CH2

OH

CH3CH

CH3

OH

CH3

CHCH3

CH2 OH

CH3C

CH3

CH3

OH

• Naming Examples

CH3

CH

CH2

CH

CH3

CH3 OH

CH3

OH

OHCH

CH3

CH3CH3 OH

4-methyl-2-pentanol or 4-methylpentan-2-ol

trans-2-methyl-1-cyclohexanol

trans-4-isopropyl-1-cyclohexanol

1-methyl-1-cyclopentanol

• Primary (1⁰) – Secondary (2⁰) – Tertiary (3⁰)

• Based on the # of Carbons Bonded to –OH containing Carbon

(1⁰) (2⁰) (3⁰)

1-carbon 2-carbons 3-carbons OH OH

OH

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• Classify and Name each of the following

• Classify each of the following

CH3 C

CH3

CH3

OHCH2 CH

CH3

OHCH3

OH

OH

OH

2-methyl-2-propanol 1-cyclobutanol 2-butanol

3° 2° 2°

2° 1°

• Multiple –OH groups? • Use “di”, “tri”, etc…

• Diol: contains 2 –OH groups

• Triol: contains 3 –OH groups

• Glycol: contains 2 –OH groups on adjacent C’s. (common name)

CH3

CH

CH2

OH

OH

CH2

CH2

OH

OH

CH2

CH

CH2

OH

OH

OH1,2-ethanediol

1,2-propanediol 1,2,3-propanetriol

Glycerin/Glycerol, & Nitroglycerin

• 1,2,3-propanetriol trinitrate • Nitroglycerin

• Alfred Nobel (1866) • Combined with clay and Na2CO3 to make TNT

CH2

CH

CH2

OH

OH

OH

+ 3HNO3

CH2

CH

CH2

O

O

O

N+

O-

O

N+

O-

O

N+

O-

O

Glycerin or Glycerol

• Nitroglycerin as an explosive • Very unstable compound

• Contains the “oxygen” needed for combustion

• Physical motion can be enough energy to start the reaction

• Nitroglycerin as a drug • Used for “Angina Pectoris”: Sharp chest pain caused by

reduced blood flow

• Mix with alcohol: relaxes the blood vessel wall

• NO group is the part that relieves the pain

• Alkene – Alcohols • “ol” given priority on carbon numbering

• Alkene second priority

• Alkane LAST priority

CH2=CHCH2OH

CH2 CH2

CH CH

CH2 CH3

OH

CH2 CH3

OH

CH3

2-propen-1-ol

3-hexen-1-ol

4-ethyl-4-penten-2-ol

• Ethers • Common name used for our class (IUPAC is different)

• Based on alkyl groups attached to the oxygen

• Alkyl groups are NOT given in alphabetical order

• Think like reading “left” to “right”

• R – O – R “name the R’s”+“ether”

Dipropyl ether? Methyl tert-butyl ether?

OO

CH3

CH

CH3

O CH2 CH3

Isopropyl ethyl ether

diethyl ether

dicyclohexyl ether

Section 13.3 continued Thiols

• Name the alkyl group attached to the –SH group

• IUPAC: same as alcohol’s but replace the “ol” with “thiol”

• Common name’s: Mercaptan’s

• Means: Mercury capturing

CH3CH2CH2CH2CH2SH

CH3

CH

CH2

CH2

CH3

SH

CH3

CH

CH

CH3

SH

CH3

2-pentanthiol 3-methyl-2-butanthiol

pentanthiol

Section 13.4 Physical Properties

• Alcohol’s • -OH “polar” nature

• Hydrogen Bonding in Alcohols – Up to 3 H-bonds per –OH group

• (1-3 carbon) Alcohols: – Soluble in Water

• Patterns & Comparisons – See following Slide

Higher bp than similar Alkane Smallest molecules have the greatest “difference” When does “Polar” –OH play a larger role in properties?

• Ethers • Polar Molecules – but Weak dipole interactions

• No Hydrogen Bonding

• Patterns and Comparisons – See following slide

CC

O

H

H

HH

H

H

Boiling Point 78⁰C

Boiling Point -24⁰C

O

HH

H

H

H

H

O

HH

H

HH

H

O

HH

H

HH

H

• Thiols • Non-Polar molecules

– Insoluble in Water

– Low BPs

• Most outstanding property is ODOR – Skunk Smell!

• Skunks? Produce these 2 thiols

CH3 CH

CH CH2

SH

CH3

CH CH2

CH2 SHCH32-buten-1-thiol

3-methyl-1-butanthiol

Section 13.5 Reactions of Alcohols

• Dehydration: acid catalyzed – H and OH are removed to form a double bond.

– Heat Required!

for activation energy! • Primary Alcohols: 180⁰C

• Secondary Alcohols: 140⁰C

• Tertiary Alcohols: 50⁰C

• Reverse of “Hydration of an alkene”

CH3

OH

H2SO4

180 °CCH2 CH2 + OH2

+ OH2OH

H2SO4

140 °C

• Dehydration Concepts • Why does dehydration need less activation energy in 3⁰

Alcohols than 1⁰?

1⁰ 2⁰ 3⁰ Ease of Dehydration

• Zaitsev’s Rule – When isomeric alkenes are obtained in dehydration, the

alkene having the greater number of carbon groups around the double bond generally dominates.

CH3

CH2

CH

CH3

OH

H3PO4

C

CH3

CH3

2-butene 80%

CH3 CH2 1-butene 20%

or

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Predict the dominate product of:

CH3

CH3

CH3

OH

OH

CH3

H2SO4

140 °C

H2SO4

140 °C

CH3CH3

CH3

CH3

• Oxidation of 1⁰ and 2⁰ Alcohols • Primary Alcohols are oxidized to “Aldehydes” and then

“Carboxylic Acids” in the presence of K2Cr2O7 or H2SO4

Ethanol Aldehyde Carboxylic Acid

[O]C

C

O

HH

H

H

H H C

C

O

HH

H

H

[O] C

C

O

O

HH

H

H

Menthol Menthone

[O]

CH3

CH3CH3

OH

CH3

CH3CH3

O

• Secondary Alcohols are oxidized to “Ketones”

• Show the Oxidation of the following • 1-hexanol

• 2-hexanol

• Cyclopentanol

• 5-methyl -5-octanol

• Ethanol and the Human Body

– As a Drug

• Depressant

• Poison – by way of reaction mechanisms

Metabolism of Ethanol Oxidized in 2 steps:

C

C O

H

HH

H

H H [O]

C

C O

H

HH

H

[O]

C

C

O

O

H

HH

H

Ethanol Acetaldehyde Acetic acid Nausea or Sweating Ethanoic acid Vomiting

• Antabuse and Alcoholics

– Prevents further oxidation of Acetaldehyde

– Blocks “Acetic Acid” Production

– Prescribed to Alcoholics

– “Hold” onto BAD symptoms of Acetaldehyde

– Condition Brain to dislike effects of Alcohol

CH3 CH2

CH3 CH2

N C

S

S

S

C

S

N

CH2 CH3

CH2 CH3

C

C O

H

HH

H

H H [O]

C

C O

H

HH

H

[O]

C

C

O

O

H

HH

H

• Ethanol and Vinegar – Ethanol and Ethanoic acid (Acetic acid – Vinegar) react to form

Ethylethanoate (an ester)

– Symptoms include excessive Vomiting – Toxic – Further Oxidation results in diethyl ether

– Symptoms include Passing Out (diethyl ether is an anesthetic) – What if you “pass out” before you “vomit”?

Produced from EXCESSIVE amounts of Alcohol in blood Stream

C

C O

H

HH

H

H H[O]

C

C

O

O

HH

HH

+CH3

CH2

O

C

CH3

O

[O]

CH3

CH2

O

C

CH3

O

CH3

CH2

O

CH2

CH3

• Blood Alcohol Levels: Testing • Oxidation of Ethanol by K2Cr2O7 (dichromate ion)

CH3CH2OH + Cr2O7-2 Cr+3

(red/orange) (green)

• Amount of “green” is used to measure relative Ethanol amounts

• 2100mL of breath contains the same amount of Ethanol as 1.00mL of blood.

H2SO4

H2O

CH3

O

OH

+

Section 13.6 Ether Reactions

• Resist Chemical Reactions – Almost Inert

• Makes them a good “SOLVENT” for organic reactions

• Won’t play a role in the reaction

• Notice how they are the “end” product of some Oxidation Reactions

Section 13.7 Thiol Reactions

• Thiols are Oxidized into disulfides

• Plays a role in PROTEIN CHEMISTRY later

2 R – SH R – S – S – R

“Thiol” “disulfide”

2 C – C – SH C – C – S – S – C – C

[O]

[Redox]

[Redox]

[O]