MATERIAL ADAPTED FROM: INTRODUCTION TO GENERAL, ORGANIC AND BIOCHEMISTRY 7 TH ED. BY: HEIN, BEST, PATTISON, ARENA ALCOHOLS, ETHERS AND THIOLS.

M A T E R I A L A D A P T E D F R O M : I N T R O D U C T I O N T O G E N E R A L , O R G A N I C A N D B I O C H E M I S T R Y 7 T H E D .

B Y : H E I N , B E S T , P A T T I S O N , A R E N A

ALCOHOLS, ETHERS AND THIOLS

FUNCTIONAL GROUPS

• Alcohols –OH group

• Phenol- OH group off of an aromatic ring

• Ethers- R-O-R, where R is an alkyl group or aromatic ring

• Aldehydes- *terminal H

• Ketones- *no terminal H

MORE FUNCTIONAL GROUPS

• Thiols- R-SH *thio means sulfur!

• Ester- R-COO-R

• Carboxylic acid- R-COOH

• Amines- R-NH2, R2NH, or R3N

• Amides- R-CON-R

CONNECTION BETWEEN ALCOHOLS, ETHERS, THIOLS AND PHENOLS

• All of these groups are derived from the structure of water, with a few substitutions.

• Alcohols- remove one H from water and add an alkyl group

• Thiols- replace the O in an alcohol with an S• Ethers- remove both H atoms from water and add two

alkyl groups in their place• Phenols- replace the alkyl group from alcohols with an

aromatic ring

• *Functional groups are important because they determine the “function” and properties of the molecule

ALCOHOLS

• Classified as primary, secondary and tertiary, depending on whether the carbon attached to the OH group is connected to 1, 2 or 3 other carbon atoms.

• Polyhydroxy alcohols or polyols- molecules that have more than 1 –OH group per molecule

PRACTICE

• For the following, determine if they are primary, secondary or tertiary alcohols:• 1) CH3OH

• 2) CH3CH(OH)CH3

• 3)CH3CH(CH3)CH2OH

• 4) CH3C(CH3)2OH

IUPAC NAMING OF ALCOHOLS

• 1) Select the longest continuous chain of carbon atoms containing the hydroxyl (OH) group.

• 2) Number the carbons so that the lowest number carbon is closest to the –OH group.

• 3) Name the parent alcohol by replacing the –e at the end of the alkane name with an –ol.

• Designate the position of the –OH group by placing the hyphenated carbon number in front of the parent alcohol name.

• 4) Name each side chain or branch alphabetically, and use numbers to designate its position off the main chain.

PRACTICE NAMING AND DRAWING ALCOHOLS

• 1)

• 2)

• 3)

• 4)3,3-dimethyl-2-hexanol

• 5) 2-ethyl-1-pentanol

• 6) 2-bromo-4-ethyl-3-heptanol

COMMON NAMES

• Alcohols have a lot of common names so it is important to recognize these for safety in lab.• Examples:• 1) isopropyl alcohol

• 2) n-butyl alcohol

• 3) sec-butyl alcohol

• 4) tert-butyl alcohol

PHYSICAL PROPERTIES OF ALCOHOLS

• High boiling points compared to their alkanes

• Example: Methane -162°CMethanol 65°C

• Boiling points of alcohols increases with the increasing number of carbon atoms.

• What part of their structure accounts for their high boiling points?

• Most are soluble in water. Solubility becomes lessened as the carbon chain lengthens. WHY?

• Predict the effect of dihydroxy alcohols on solubility in water.

ACIDIC/BASIC PROPERTIES OF ALIPHATIC ALCOHOLS

• Similar to water… which is amphiprotic or amphoteric, which means it can act as an acid OR base in solution.• In strong acids, it will

accept a proton and become an oxonium ion.

• Small alcohols, like methanol and ethanol, have same acid strength as water. Larger acids are weaker.

REACTION WITH ALKALI METALS

• Just like water, alcohols react with group 1 metals to form an anion and hydrogen gas.

• Example: 2 CH3CH2OH + 2 Na 2 Na+ + -OCH2CH3 + H2(g)

• The resulting anion is called an alkoxide ion (RO-) and is a stronger base than hydroxide! These are used in industry when a strong base is required.

• Primary>secondary>tertiary alcohols as far as reaction with sodium and potassium. As molar mass of alcohol increases, the reactivity decreases.

OXIDATION OF ALCOHOLS

• Carbon atoms exist in progressively higher stages of oxidation in different functional groups:

Alkanes Alcohols aldehydes and ketones carboxylic acids carbon dioxide

• Converting alcohols to aldehydes, ketones and carboxylic acids allows scientists to make plastics, antibiotics, fertilizers, etc.

• Common oxidizing agents: oxygen from the air, KMnO4 in basic solution, K2Cr2O7 in acidic solution.

OXIDATION OF ALCOHOLS

Source: http://dwb4.unl.edu/Chem/CHEM869E/CHEM869ELinks/www.siue.edu/~rdixon/classes/chem120b99/lectures/chpt-14/chpt-14.html

PRACTICE

• 1) Determine the products when the following react with potassium dichromate and concentrated sulfuric acid:• A) 1-propanol

• B) 2-propanol

• C) cyclohexanol

DEHYDRATION OF ALCOHOLS

• 2 types:• 1) Intramolecular dehydration of alcohols forms alkenes• Sulfuric acid is used as well as heating up the reaction• Water is removed from a single alcohol molecule• Secondary and tertiary alcohols yield alkenes• If there are two neighboring carbons that have hydrogens

that may leave with the OH group, follow Saytzeff’s rule.• Saytzeff’s rule: If there is a choice of positions for

the carbon-carbon double bond, the preferred location is the one that gives the more highly substituted alkene.

• Example: 2-butanol 2-butene + 1-butene

DEHYDRATION OF ALCOHOLS

• 2) Intermolecular dehydration of alcohols forms ethers• Two alcohol molecules come together, eliminate

water and form an ether…(called a condensation reaction)• ONLY works for primary alcohols!!!!• Depends on temperature and number of reactant

molecules…lower temps and higher concentration of alcohol yield ethers.

ESTERIFICATION

• Alcohols can react with carboxylic acids to form esters and water.• Important reaction…discussed more in later

chapter.

Photo Source:http://chempaths.chemeddl.org/services/chempaths/?q=book/General%20Chemistry%20Textbook/1352/properties-organic-compounds-and-other-covalent-substances&title=CoreChem:Esters

HYDROXYL GROUP IMPORTANCE

• The –OH group is a gateway to many organic reaction AND biochemical reactions as well.• Example: Fats are degraded from alkanes to

alkenes…then hydrated to form an alcohol.• Then, the alcohol is oxidized to form a ketone.

This process is necessary to use energy from fats.• 10% of infants that die of SIDS cannot degrade

fats. It is hypothesized that this lack of ability to use fat for energy may be a leading cause of SIDS.

MAKING ALCOHOLS

• Generally, the reverse of the reactions that we have discussed so far are the ones used to make alcohols.• 1) Hydrolysis of esters

• 2) Alkaline hydrolysis of an alkyl halide (primary and secondary alcohols only)

• 3) Catalytic reduction of aldehydes and ketones to make primary and secondary alcohols.

• These starting materials are expensive, so specific methods are devised for specific alcohols.

METHANOL

• Used to be made by heating wood in a non-oxygen atmosphere…called destructive distillation.• Early 1920s, began catalytic hydrogenation of

carbon monoxide…• CO + 2 H2 CH3OH

• Requires catalysts, high temp and high pressure• Can be made from coal as well, significant as a

non-petroleum source• Is useful in conversion to manufacture of other

chemicals, polymers, etc.

ETHANOL

• Aka: grain alcohol, ethyl alcohol, spirit• Earliest and most widely known alcohol• Prepared by fermentation of starch and sugar (for

drinking)• Pure ethanol is hygroscopic (water seeking), reaches

equilibrium at 95.6% ethanol.• For industrial uses, it is made by acid-catalyzed

addition of water to ethylene.• Uses: intermediate in manufacture of acetaldehyde,

acetic acid, ethyl acetate and diethyl ether• Ethanol for industrial use is usually denatured by

adding small amounts of methanol and other chemicals that are hard to remove and cannot be consumed.

ISOPROPYL ALCOHOL (2-PROPANOL)

• Synthesized from propene and water, catalyzed by acid…2 propanol, not 1-propanol, is produced because of Markovnikov’s rule.

• Low-cost alcohol, used in production of acetone• Principle component in rubbing alcohol• Also used as an industrial solvent

ETHYLENE GLYCOL (1,2-ETHANEDIOL)

• Simplest alcohol containing 2 –OH groups• Prepared from ethylene, derived from petroleum• Common uses:• Preparation of synthetic fibers such as Dacron

and Mylar• Major ingredient in “permanent” antifreeze for

vehicles• As a solvent in paint and plastics industries• In the formulation of printing ink and ballpoint

pen ink• EXTREMELY TOXIC IF INGESTED!!!!!

GLYCEROL (1,2,3-PROPANETRIOL)

• Also known as glycerine• Syrupy liquid with a super sweet taste, about 0.6 times

as sweet as cane sugar.• It’s a by-product of processing animal and vegetable

fats to make soap and other products.• Made commercially from propene• Uses:• Raw material in manufacture of polymers and

explosives• An emollient in cosmetics• Humectant in tobacco products• Sweetener

PHENOLS

• Naming:• Most are named as derivatives of the parent

compound, much like aromatics• Para, Meta and Ortho apply here too• Examples:

A FEW COMMON PHENOLS

Vanillin

PROPERTIES OF PHENOLS

• In its pure state, phenol is a colorless, crystalline solid with a melting point at 41°C and a characteristic odor.• Highly poisonous…can cause nausea, vomiting

and death from respiratory collapse.• Weak acid…• Widely used as an antiseptic and disinfectant…

one of the first used in hospitals as a disinfectant.

MAKING PHENOLS

• Benzene and propene are mixed in the presence of acid to form cumene.• Cumene is then oxidized to form cumene

hydroperoxide, which is then treated with dilute acid to form phenol and acetone.

ETHERS

• IUPAC rules for naming ethers:• 1) Select the longest carbon chain and label it with

the name of the corresponding alkane.• 2) Change the –yl ending of the other hydrocarbon

group to –oxy to obtain the alkoxy group name.• Examples: CH3O- methoxy

• CH3CH2O- ethoxy

• Phenyl phenoxy• 3) Combine the two names from step 1 and 2, giving

the alkoxy name and its position on the longest carbon chain first, to form the ether name.

PRACTICE

• 1)

• 2)

• 3)

• 4) ethoxyethane

• 5) 2-methyl-2-propoxy-2-methylpropane

• 6) ethoxybenzene

STRUCTURES AND PROPERTIES OF ETHERS

• Ether molecules have a bent shape, much like that of water.

• More polar than alkanes, but less polar than alcohols, since no H is attached to the O.

• Can hydrogen bond with water molecules and acids, which accounts for its solubility in these substances.

• Ethers are very good solvents for organic compounds. Both polar and nonpolar substances can dissolve in ethers.

• Little chemical reactivity, but they have a great value as solvents.

• Use can be dangerous because of their volatility and creation of explosive vapors with air.

• Oxygen slowly reacts with ethers to form unstable peroxides.

PREPARATION OF ETHERS

• Intermolecular dehydration of alcohols- (we already did this!)• Williamson synthesis-

alkyl halides can react with sodium alkoxides• The alkyl halide can

be primary or methyl but NOT secondary or tertiary.

• The alkoxide can be methyl, primary, secondary, or tertiary.

• Write equations for the preparation of:• A) 1-propoxybutane

B) Methyl phenyl ether

C) Benzyl ethyl ether

THIOLS