Chapter 10 Structure and Synthesis of Alcohols

Alcohols

They are polar with hydrogen bonds (with Hydroxy OH group)

Primary Alcohol

Structure with Oh and 1 r group

Secondary Alcohol

Structure with Oh and 2 r groups

Tertiary Alcohol

Structure wth OH and 3 R groups

Phenol

Cyclohexene with OH attached (EXTREMLEY ACIDIC)

IUPAC nomenclature of Alcohols

Find longest carbon chain with the OH group

• number the chain starting form the end closest to the Oh group group

• ending name with ol not e

Glycols

Cyclohexane with 2 adjacent hydroxy -oh groups

Naming Phenols

OH group is assumed to be on carbon 1

Alcohol Physical Properties

Have High boiling points = due to the hydrogen bonding

• alkyl group size increases—> alcohol solubility decreases

Acidity of Alcohols

large pKa of 15.5-18 = weak acid

• alkyl group increases = acidity decreases

• Added halogens = increases acidity

Alchol Acidity by Classification: Primary alcohol (1°) > Secondary (2°) > Tertiary (3°)

Sodium Alkoxides formation

A primary alcohol reacts with NA to form an IRREVERSIBLE primary alkoxide

• alkoxide: R-OH

Potassium Alkoxides

Secondary or Tertiary alcohol reacts with P to form an IRREVERSIBLE secondary or tertiary alkoxide

• alkoxide: R-OH

Phenoxide Ion Formation

Phenol reacts with a strong base + -OH (ex, Na+ -OH) to form a phenoxide ion

SN2 Nucleophilic Substitution on an Alkyl Halide

Alkly Haldie + Nuc (OH) —> PrimaryAlcohol + x-

It is the same process of SN2 substitution but only using the specific substrate of an alkyl halide

Acid-Catalyzed Hydration of an Alkene (OR JUST ALKENE HYDRATION)

alkene + H20 —> H2so4, h202, or h3Po4

• the acids (H+) are the H2SO4, H2O2 and H3PO4

• markovinkov

Oxymercuration-Demercuration

Alkene + HgOAC2 —> H2O, H2O —> NABH4

• markovinkov

Hydroboration-Oxidation (Or just Hydroboration mechanism)

Alkene + BH3.THF —> H20 (or H2O2, NAOH, -OH dilute BH2 to OH)

• syn addition and antimarkovinkov

B2H6 can be used instead of BH3.THF

When mechanisms form 1,2-diols formed from alkenes

Two types of 1,2-diols: Antio diol and Syn diol

Antio Diol: Formed through epoxidation

• alkene + Peroxyacid —> H+ —> H2O, H2O

Syn Diol: Formed through Synhydroxylation

• Alkene +OsO4 —> H2O2 or KMnO4 or -OH

Acetylide Addition to Carbonyls

Acetylide + Ketone (or an aldehyde —> H3O+ —> forms acetylenic alcohol

Organometallic Reagents 

The bond between a carbon and a metal (ex: C-LI)

• carbon is more e- neg than most metals

• when the bond is formed, e- density moves towards the cabron

  • carbon becomes full with e- (becomes partial neg) and the metal lacks e- (becomes partial pos)

  • carbon w/ partially neg charge allows it to act nucleophilic

    • carbon ready to attack poor electron atoms (give its e- density away

CARBON IN ORGANOMETALLIC REAGENTS IS NUCLEOPHILIC

• Carbon is partial neg, wants to donate e- density

Grignard Reagents

Alkyl Halide (R) - X + Magnesium Metal (Mg) —> ether —> R-MgX

• it is stabalized by an ether solvent

• The heaver the halide attaches is = the more reactive

  • heavier halide attached = increased reactivity

Grignard Regeant: R-Mg-X

• heaver X = more reactive

• The R group can be ANYHALIDE (PRIM, SEC, TERT, VINYL, ARYL

Organolithium Regeanets

Alkyl Halide (R-X) + Lithium (2 Li ) —→ Aprotic solvent —> R-LI + LiX

Regeant: R-Li 

• can be formed using any type of alkyl halide (R)

Grignard Reagent Reaction with Carbonyl

Grignard Regenat (R-MgX) + Carbonyl (Ex: Ketone or Aldehyde)

Phenylmagnesium Bromide reacting with carbonyl compound

It is the same mechanism as the grignard regeant reacting with a carbonyl compound

• Only now one of the r groups attached is a phenol

  

Synthesis of Primary (1° Alcohols)

Overview: Grignard + Carbonyl —> Alcohol

Griganrd + FORMALDEHYDE —> 1° ALCOHOL

• 1° alcohol = Only one R group (the OH in this synthesis)

  

Synthesis of Secondary (2° Alcohols)

Overview: Grignard + Carbonyl —> Alcohol

Grignard + ALDEHYDE —> 2° alcohol

• 2° alcohol = 2 R groups (CH3 and OH)

  • ch3 can be any type of R not only ch3

Synthesis of Tert (3° Alcohol)

Overview: Grignard + Carbonyl —> Alcohol

Grignard + Ketone —> Tert Alcohol

• 3 R groups (Ketone’s Rs and Grignard’s OH)

  

Grignard Regeant + Acid Chloride

2 Moles of Grignard Regeants are used in this reaction

• 1 Grig used to start 2nd grig used to react with ketone intermediate

Grid + Acid Chloride —> ether —> Ketone Intermediate

grig +Ketone Intermediate —> H3O+ —> Tert alcohol

• ch3 of acid chloride can be any alkyl halide (r group)

Grignard Regeant + Ester

2 Moles of Grignard Reagent Used

• One to Start attack on Ester the 2nd to attack the ketone intermediate

• Forms tertiary alcohol

  

Ehtylene Oxide Ring Opening

Grignard + Ethylene Oxide —> EthyleneoxideOH (Primary alcohol)

• Ring + 2 addition cabrons (OH) product

  • primary alcohol

Organometallic Reagents Limitations

C-Metal —> The C in the regeant acts as a nucleophile becasue it is more e- neg than most metals

• the C wants to donate e- to e-poor species

C-Metal Cant react with acidic protons (H+ donators) and Electorphilic multiple bonds (pos)

• With acidic protons —> the C will instantly react to obtain an H+ —> C-Metal becomes a usless alkane

• With Mutliple bond speicies—> the speicies are slightly pos which the C wants to react with and destroy the grignard

Acidic Protons (O-H, N-H, S-H),

Electrophilic

Multiple Bonds (C=N, S=O, N=O)

What Hydride Reageants Reduce Carbonyl Groups to 1° and 2 alcohols

lithium alumnum hydride and sodium borohydride

• both react in the same manner of Grig reagant + carbonal (attack the c and attaches)

• If carbonyl is aldehyde —> 1° alcohol formed

• If carbonyl is ketone —> 2° alcohol formed

Both Lithium alumnimum hydride and sodium borohydride attack and attach as an H group

Sodium Borohydride vs Litium Alumnium Hydride as a reducing agent

Sodium Borohydride

• only redues ketones and aldehydes carboxyls

• weaker reducing agent

Lithium Alumnium Hydride

• reduces everything (ketones, aldehydes, esters, and carboxylic acids)

• is a stronger reducing agent

Sodium Borohydride

Weaker Ruducing agent (only reacts with ketones and aldehydes)

When reducing, does the same process as grig +carbonyl but instead of attaching an r grouop it attaches an H+

• it also doesn’t use 2 moles

• with aldehydes —> 1° alcohol

with aldehydes —> 1° alcohol

with ketones —> 2° alcohol

Lithium Aluminum Hydride

Stronger reducing agent (reduces everything: ket, alde, esters, & carboxylic acids)

• alde —> 1° alcohol

• ket —> 2° alcohol

• esters & carboxylic acids —> 1° alcohol

Same process as grig + carbonyl (but instead of attaching R it attaches an H+)

• it also doens’t use 2 moles

Catalytic Hydrogenation

Ket or alde + 2H2 + Acid Catalyst —> reduces to a 2° or 1° alcohol

• reduces C=O bond

• and C=C bond

Ket or alde + NABH4 —> reduces to a 2° or 1° alcohol

• reduces C=O bond

Thiols

Configuration where SH is written instead of OH

• sulgar analogues (S—> O)

They are more acidic than alcohols (lower pka than alcohols)

Phenol > Thiols > Alcohols in terms of acidity

IUPAC: written on the end of an alkane (ex: ethanethiol)

Thiol Synthesis

NaSH + RX —> R-SH + NaX

• Na+ SH reacts with a primary alkyl halide (unhindered, RX)

• Produces the thiol: R-SH)

Thiol Oxidation

Thiol: R-SH

It is easily oxidized into disulfides (R-S-S-R)

2 Molecules of Thiol + Oxidizing agent —> R-S-S-R

Thiol Oxidation to Sulfonic Acid

Thiol (R-SH) can be oxidized via KMnO4 or HNO3 into a sulfonic acid

• results in an expanded octet (the sulfonic acid) —> that can then show charge separation (+ and - charges)