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54 terms

#14 Alcohols, Phenols & Ethers

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alcohols
- an organic compound in which an -OH group is bonded to a saturated carbon atom
- General formula = R-OH
-OH group is the functional group
-OH group in alcohols is covalent, not ionic
3 simplest alcohols
1. methanol CH₃-OH
2. ethanol CH₃-CH₂-OH
3. propanol CH₃-CH₂-CH₂-OH
Common names for alcohol (C₁-C₄)
1. name carbon atoms as a alkyl group (ex. methyl, ethyl, etc.)
2. add alcohol with a space btw (ex. Methyl alcohol)
IUPAC Rules for alcohol
1. name longest C chain to which -OH is attached
-drop the "e" and add "ol" (ex. methane -> methanol)
2. number chain closest to -OH. Indicate number position of the -OH. -OH has highest priority.
3. name & number other substituent
4. in a ring -OH is assumed to be on carbon 1, so numbering the -OH is not necessary
polyhydroxy alcohols naming
2 = diol
3 = triol
keep the "e" ex. 1-2-ethanediol,1-2-propanetriol
isomerisms for alcohols - 2 types
constitutional (both positional & structural) isomers are possible if 3 or more carbons
1. Positional = same carbon chain, position of -OH group is different
2. Structural = different carbon chains
C₅ isomers
total of 8
3 are pentanol positional
4 methylbutanols positional
Methyl alcohol (Methanol) -formula, using, how made & toxicity/oxidized
1. CH₃-OH
2. race cars, solvent in paint
3. aka wood alcohol
4. made from H₂ & CO
5. Toxic --> oxidized to formaldehyde & formic acid
6. treated w/ethanol. ethanol oxidized first
Ethyl alcohol (Ethanol) - formula, uses, how made & toxicity/oxidized
1. CH₃-CH₂-OH
2. fermentation of grains (aka grain alcohol), plant sugars. Use yeast to ferment. 18%
3. industrial make by hydration of ethylene
4. excellent solvent, used more as gas additive
5. distributed as denatured alcohol = toxic subst.added
6. oxidized to acetaldehyde --> hangover. birth defects, liver damage
Isopropyl alcohol (2-propanol) - formula, uses, toxicity/oxidized
1. CH₃-CH(CH₃)-OH
2. rubbing alcohol - cools body temp
3. twice as toxic as ethyl alcohol
4. bitter, so throw up before fatal
5. oxidized to acetone
Ethylene Glycol
1. CH₂(OH)-CH₂(OH) (1,2-ethanediol)
2. Diol with 2 -OH groups attached on two adjacent carbon atoms
3. synthesized from ethylene
4. colorless and odorless, miscible w/water
5. antifreeze & plane deicer
6. extremely toxic ---> oxidizes to oxalic acid
Propylene Glycol
1. CH₃-CH(OH)-CH₂(OH) (1,2-propanediol)
2. Diol with 2 -OH groups attached on two adjacent carbon atoms
3. widely used in drugs as solvent
4. nontoxic ---> oxidized to pyruvic acid
Glycerol
1. CH₂(OH)-CH(OH)-CH₂(OH) (1,2,3-propanetriol
2. a triol w/three -OH groups attached on 3 adjacent carbon atoms
3. clear thick liquid, byproduct of fat metabolism
4. skin lotions & soaps
Alcohol properties - polar or non-polar
1. -OH is polar, alkyl group is nonpolar
2. length of nonpolar chain or # of hydroxyl group dominates
3. small monohydroxy alcohols are soluble in water. more than 3 carbons then solubility ↓
Alcohol properties - boiling points
1. 1-alcohol = BP ↑ as length of carbon chain ↑
2. more than 1 hydroxyl group BP ↑
alcohols & hydrogen bonding
1. hydrogen bonding respons. for physical property differences btw alkanes & alcohols
a. ↑ BP b/c of hydrogen bonds
b. ↑ solubility in H₂O b/c of hydrogen bonds
preparation of alcohol (2)
1. unsymmetrical addition = hydration of alkenes (sulfuric acid is the catalyst. Markovnikov's rule determines the predominant alcohol product
2. addition of H₂ to a carbonyl group (C=O). 1 hydrogen added to carbon and 1 to oxygen to form OH
alcohol classification (3 types)
1. primary (1°)= the hydroxyl bearing carbon is bonded to one other carbon
2. secondary (2°) = the hydroxyl bearing carbon is bonded to two other carbons
3. Tertiary (3°) = the hydroxyl bearing carbon is bonded to three other carbons
alcohol classification chemical reactions
1. dependent on type of alcohol 1°, 2°, 3°
2. more alkyl groups around C-OH ↓ hydrogen bonding
Alcohol chemical reactions (4)
1. combustion = CO₂ + H₂O
2. dehydration
3. oxidation
4. halogenation
intramolecular dehydration
-reaction that occurs w/in the alcohol molecule
-dehydration reaction in which the components of water (H & OH) are removed from a single reactant
-aka elimination reactant
-replace alcohol functional group w/a double bond → product is an alkene (DB). the result can be more than 1 type of alkene product, b/c H loss can occur from either neighboring carbon atom
-need H₂SO₄ & 180°C as catalyst
Zaitisev's rule
the major product in an intramolecular alcohol dehydration reaction is the alkene that has the greatest number of alkyl groups attached to the C atoms of the double bond
intermolecular dehydration
1. reaction that occurs between 2 alcohol molecules (aka condensation reaction)
2. two molecules of alcohol combine to form ether.
3. catalyst = H₂SO₄ + 140°C
4. useful yields for primary alcohols. secondary & tertiary yield alkenes
ex. CH₃-CH₂-O-H + H-O-CH₂-CH₃ →CH₃-CH₂-O-CH₂-CH₃ + H₂O (ethanol + ethanol)
oxidation
1. ↑ the number of C-O bonds and/or ↓ the number of C-H bonds
2. addition of oxygen or removal of hydrogen. removal of 2 hydrogen, one from -OH & other from the carbon the -OH was attached to.
3. use mild oxidizing agents
4. only primary or secondary alcohols can be oxidized
product of primary alcohol oxidation
primary→aldehdye→carboxylic acid
product of secondary alcohol oxidation
secondary→ketone
organic reduction
a reduction that ↓ decreases the number of C-O bonds and/or ↑ the number of C-H bonds
halogenation of alcohol
1. halogen (ex. Cl, Br) is substituted for the -OH group producing an alkyl halide
2. alkyl halide superior to alkyl halide (thru halogenation of alkane)
polymeric alcohols
1. are possible
2. most common = polyvinyl alcohol, which is soluble in water
phenol
an organic compound in which an -OH group is attached to a carbon atom that is part of an aromatic carbon ring system.
AR-OH
aryl group
an aromatic carbon ring system from which one hydrogen atom has been removed
AR-OH
phenol naming
name is phenol, -OH group doesn't have to be numbered, assumed in 1 position.
ex. phenol, 3-bromophenol
methylphenols
1. ortho-Cresol
2. Meta-cresol
3. para-cresol
hydroxy phenols
1. catechol (1,2 position)
2. resorcinol (1,3 position)
3. hydroquinone (1,4 position)
phenol physical characteristics
1. low melting solids or oily liquids
2. sparingly soluble in water
3. antiseptic or disinfectant properties
acidity of phenols
1. weak acids in solution
2. Ka value = 10⁻¹⁰
uses for phenol
1. antiseptic (mouthwash, lozenges, lysol)
2. antioxidant (food preservation, vitamin E)
3. from plants = flavoring agents (vanilla) or antibacterial
ether
1. an organic compound in which an oxgen is bonded to 2 carbon atoms by single bonds.
2. formula R-O-R
3. R can be an alkyl, cycloalkyl or aryl groups
4. similar structure to water
ether: common names
Common names = aklyl groups with 4 or fewer carbon
name the 2 hydrocarbon groups attached to oxygen and add ether at the end.
1. If unsymmetrical, list group alphabetically and add ether (Ex. ethyl methyl ether, butyl ethyl ether)
2. If symmetrical, use di with the group name and add ether (Ex. dimethyl ether)
alkoxy group
is an OR (oxygen and alkyl group) group, an alkyl (or aryl) group attached to an oxygen atom
ether: complex naming
1. longest chain is the base name (from either side of the oxygen)
2. change the "-yl" ending to "-oxy" (ex. methyl→methoxy)
3. place the alkoxy, name with a locator number, in front of the base chain name
isomerism for ethers
depend on:
1. partitioning of carbon atoms btw the 2 alkyl groups
2. isomerism possibilities for the individual alkyl groups
3. no isomers for C₂-C₃
functional group isomerism
ethers and alcohols w/the same number of carbon atoms & same degree of saturation = same molecular formula (ex. dimethyl ether & ethyl alcohol) → constitutional isomers (aka functional group isomers)
functional group isomers
constitutional isomers that contain different functional groups
ethers: physical properties
1. BP, w/similar molecular mass, are comparable to alkanes and much lower than alcohols.
a. alcohol can H bond to each other, but alkanes and ethers cannot
b. ethers can H bond to water
2. solubility = ethers more soluble than alkanes, b/c they can H bond to water
3. most common ethers are liquid
ether: chemical properties
1. flammable
2. react slowly with oxygen
3. unreactive towards acid, bases & oxidizing agents → good solvents
4. undergo halogenation reactions
cyclic ethers
1. contain the ether functional groups as a part of ring system (heterocyclic organic compounds)
2. THF & Furan = 5 member rings
3. Pyran = 6 member ring
heterocyclic organic compounds
a cyclic organic compound in which one or more of the carbon atoms in the ring have been replaced with atoms of other elements
sulf-hydryl group
1. -SH functional group
2. thiol functional group is called the sulfhydryl group
thiol
1. is an organic compound in which a sulfhydryl group is bonded to a saturated carbon atom
2. the sulfur analog of alcohols - contain -SH functional groups instead of -OH
3. R-SH = thiol
4. R-S-R = thioether
thiol: naming
1. same as alcohol except "-thiol" instead of '-ol" (ex. butanethiol)
2. with diols & triols, keep the "e" at the end (ex. propanethiol)
thiol: physical properties
1. ↓ BP than alcohols b/c lack of hydrogen bonding
2. strong disagreeable odor (natural gas & skunks)
thiols: oxidation
1. lead to disulfide (S-S)
Ex. R-SH +SH-R → R-S-S-R + H₂O
thioether (aka sulfides)
1. an organic compound in which a sulfur atom is bonded to 2 carbon atoms by single bonds
2. R-S-R
3. strong odor
4. dimethyl sulfide is gas, ethyl methyl sulfide is liquid
5. thiols and thioethers exhibit functional group isomerism like alcohols & ethers