L.10 Alcohols

Question 1

Alcohols

General Form

Pka

Group

Suffix

Prefix

Priority

Answer 1

• ROH
• pKa = 16
• Group = hydroxyl (-OH)
• Suffix = -ol
• Prefix = Hydroxy-
• Higher priority than double or triple bonds and alkanes
• Diols = Two hydroxyls, geminal same carbon -or- vicinal if on adjacent

Question 2

Structure of a PHENOL

Answer 2

Benzene Rings with Hydroxyl Groups

Question 3

How are Phenols Named?

Answer 3

Phenols are named by their relative position of the hydroxyl groups with any other attached molecule.

ortho- ADJACENT

meta- SEPARATED BY 1 CARBON

para- ON OPPOSITE SIDES OF THE RING

Question 4

Physical Properties of Alcohols & Phenols

Answer 4

Alcohols; hydrogen bonding ( F O N ) raises their boiling/melting points relative to there corresponding alkanes. Also increases solubility.

Phenols; hydrogen on the phenol is more acidic b/c the electron on the oxygen is resonance stabilized by the benzene ring. (Aromatic ring can delocalize the charge of the conjugate base)

Electron-donating groups like alkyl groups decrease acidity because they destabilize negative charges. Electron-donating groups, such as electronegative atoms and aromatic rings, increase acidity because they stabilize negative charges

Question 5

Oxidation Reactions of 1°ALCOHOLS

Answer 5

1° Alcohols

PCC (mild oxidant) = Aldehyde

Chromium (strong) = Carboxylic Acid

Jones Oxidation CrO₃ + H₂SO₄ + Acetone (strong) = Carboxylic Acid

Question 6

Oxidation Reactions of 2º ALCOHOLS

Answer 6

2º Alcohols

PCC (mild) = Ketones

K/Na₂Cr₂O₇ + H₂SO₄ (stong) = Ketones

CrO₃ + H₂SO₄ + Acetone (strong) = Ketones

Question 7

Oxidation Reactions of 3º Alcohols

Answer 7

Cannot be further oxidized

Question 8

What are Mesylates & Tosylates?

Answer 8

Alcohols can be converted to mesylates and tosylates to make them better-leaving groups for nucleophilic substitution reactions.

Mesylates contain the functional group -SO₃CH₃, which is derived from methanesulfonic acid.

Tosylates contains the functional group -SOC₆H₄CH₃, which is derrived from toluenesulfonic acid.

Question 9

Explain the conversion of alcohols into protecting groups.

Answer 9

• Two equivalents of alcohol or a dialcohol can be reacted

with the carbonyl of an aldehyde or ketone to

form an ACETAL or KETAL respectively.

• Then, other groups in the compound can be reacted (especially by reduction with Lithium aluminum hydride ) without affecting the newly formed acetal or ketal.
• The acetal or ketal can be regenerated back to carbonyls with

catalytic acid, which is called deprotection.

Question 10

How are QUINONES produced?

Answer 10

• Phenol + Oxidizing Agents = Quinones
• Quinones are resonance-stabilized electrophiles
• Vitamin K1 (phylloquinone) & K1 (menaquinone) are examples of biochemically relevant quinones.

(photosynthesis + carboxylation of blood clotting factors)

Question 11

What is UBIQUINONE? & How is it useful?

Answer 11

Ubiquinone, also known as COENZYME Q is a biologically active quinone that acts as an electron acceptor in complexes I II & III of the electron transport chain.

Thus,

It is reduced to UBIQUINOL, which is an electron carrier within the phospholipid bilayer (long alkyl chain = lipid soluble)

Question 12

Can Quinones be further oxidized?

Answer 12

Yes, they are further oxidized to form HYDROXYQUINONES.

• Used for the synthesis of medications
• Two carbonyls + HYDROXYL GROUP
• Less electrophilic, but still very reactive

2-HYDROXY-1,4-BENZOQUINONE

(If more than one hydroxyl group then, di-, tri-, etc.)