13-1 Principles and Applications of Inorganic, Organic, and Biological Chemistry Denniston, Topping,...
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Transcript of 13-1 Principles and Applications of Inorganic, Organic, and Biological Chemistry Denniston, Topping,...
13-1
Principles and Applications ofInorganic, Organic, and
Biological ChemistryDenniston, Topping, and Caret
4th edChapter 13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Power Point to Accompany
13-2
FormulasAlcohols have the general formula R-OHEthers have the formula R-O-R
R can be aliphatic or aromaticPhenols have the formula Ar-OH
Ar must be an aromatic ring (eg. Benzene)
Thiols have the formula R-SHDisulfides have the formula R-S-S-R
R may be aliphatic or aromatic
13-3
13.1 Alcohol: Structure and Properties
Low molecular weight alcohols (up to 5-6 carbons) are soluble in water because they are polar and hydrogen bond (through the OH) with the water molecule.
Eg. CH3CH2OH solube but CH3OCH3 barely
soluble.
CH3CH2CH2CH2OH, 7 g per 100 mL but
HOCH2CH2CH2CH2OH is very soluble!
(two OH groups)
13-4
Alcohol Boiling PtsAlcohols have abnormally high bp
relative to their molecular weights due to their ability to hydrogen bond.
CH3CH2OH
CH3CH2O
H
CH3CH2OH
13-5
Alcohol Boiling Pts-2
Trends in boiling points (Similar MW)
CH3CH2OH
CH3O CH3
CH3CH2CH3 bp -42 oC
bp -23 oC
bp +78.5 oC
13-6
13.2 Alcohols: Nomenclature
IUPAC: based on the longest chain containing the OH carbon.
The e of the alkane name is replaced with ol. The chain is numbered from the end giving the OH carbon the lower number. The name is prefixed with the number indicating the position of the OH group.
For cyclic alcohols, the OH is at C-1.
13-7
Alcohols: names-2
Name the alcohols.
CH3CHCHCH3OH
CH3
OH
CH3
3-methyl-2-butanol3-methylcyclohexanolOH must be at C-1
13-8
Alcohols: names-3The common names for alcohols consist
of the alkyl group name, a space, and the word alcohol. Name:
CH3 C CH3
CH3
OHCH3CH CH3
OHt-butyl alcohol isopropyl alcohol
13-9
13.3 Alcohol Examples of Interest
CH3CH2OHethyl alcohol(drinking alcohol)
OH CH2CH2OHethylene glycol(antifreeze)
OH CH2CH CH2OHOH
glycerol(in fats,a moisturizer)
13-10
13.4 Classes of Alcohols
CH3CH2OH
CH3CH CH3OH
CH3 C CH3
CH3
OH
Primary: one R group on alcohol C
Secondary:Two R groups on alcohol C
Tertiary:Three R groups on alcohol C
13-11
13.5 Reactions Involving Alcohols: prep
1. Form alkenes by adding water (hydration)
CH3 CH CH2
CH3 CH CH3
OH
H2O, H+
CH3 CH2 CH2
OH
Major Product
13-12
Alcohols Rxns: prep2. Form aldehydes/ketones by reduction
hydrogenation with H2.
CH3 C CH3
OCH3 CH3
OHCH
H2, Pt/Pd/Ni
CH3 C HO
CH3
OHCH2
H2, Pt/Pd/Ni
2o
1o
13-13
Alcohols: reactions1. Alcohols dehydrate with heat and strong
acid to give alkenes. Zaitsev’s rule (most substituted alkene) applies to determine the major product.
CH3CHCH CH3
OH
CH3warmH2SO4 or
H3PO4
CH3C CH CH3
CH3
CH3CHCH CH2
CH3
Major product
Minor product
13-14
Alcohols: reactionsZaitsev’s rule applied again
CH3
OH
CH3
major product:more substitutedalkene
warmH2SO4 orH3PO4
H may leave from
13-15
Alcohols: reactions
2. Oxidation
Secondary alcohols oxidize to ketones. (The reaction is also an elimination of 2H.)
The usual oxidizing agent is a Cr(VI) species.
Tertiary alcohols do not oxidize as there is no H on the carbonyl carbon to remove!
OH CrO3, py orK2Cr2O7
O
2H eliminated
13-16
Alcohols: reactionsPrimary alcohols usually oxidize to
acids. With some care (Usually CrO3)
an aldehyde may be obtained.
CH3CH2CH2OH
CH3CH2CHO
CrO3, py
KMnO4CH3CH2C
OOH
[O]
[O]
Easily oxidizedto acid
13-17
13.6 Redox in Living SystemsOxidation-gain of oxygen
loss of hydrogen (usually 2)
Reduction-loss of oxygen
gain of hydrogen (usually 2)
R CH
HH
R CH
OHH
R CH
O R COH
O
More oxidized form
More reduced form
13-18
Biological Redox-2Oxidoreductases catalyze biological
redox reactions. Coenzymes (organic molecules) are required to donate or accept hydrogen.
NAD+ is a common coenzyme.
O CCOO
-
HCH2COO
-
H OCCOO
-
CH2COO
-
+ NAD+
Malatedehydrogenase
+ NADH + H+
13-19
13.7 PhenolsWidely used as health care germicides andas flavors and preservatives.
Thymol
(mint)
CH3
OHCHCH3CH3
OH
CH3
p-cresolin Lysol
OH
CH2
OHCH35
hexyl resorcinolin throat lozenges
13-20
13.7 Phenols-2
Phenols are acidic but not as acidic as carboxylic acids. They react with NaOH to give salts and water. (Acid/base chapter.)
Note: alcohols are not acidic in the context of our class.
OH+NaOH
ONa
+H2O
13-21
13.8 Ethers
Ethers are slightly polar but do not hydrogen bond to one another.
Trends in boiling points (Similar MW)
CH3CH2OH
CH3O CH3
CH3CH2CH3 bp -42 oC
bp -23 oC
bp +78.5 oC
13-22
Ethers: namesCommon names for ethers consist of the
names of the two groups attached to the O listed in alphabetical order (or size) and followed by ‘ether’. Each part is a separate word. Name:
CH3 CH O
CH3
CH3
CH3CH2O
Isopropyl methyl etherethyl phenyl ether
13-23
Ethers: names-2
The IUPAC names for ethers are based on the alkane name of the longest chain attached to the O. The shorter chain is named as an alkoxy substituent. (alkane with the ane replaced by oxy, eg. CH3CH2O=ethoxy)
Thus CH3CH2CH2CH2CH2-O-CH3
1-methoxypentane
13-24
Ethers: reactions
• Chemically ethers are moderately inert
• Symmetrical ethers may be prepared by dehydrating two alcohol molecules
CH3 CH2O CH2 CH3
CH3 CH2OH CH3CH2OH
H+ (H3PO4) warm
13-25
Ethers: uses
Ethers are often used as anesthetics.
CH3 CH2O CH2 CH3Diethyl etherFirst successfulgeneral anesthetic
CH3O C C HF
F
Cl
Clpenthrane
13-26
13.9 Thiols: names
Named based on longest alkane chain with the suffix thiol position indicated by number. E. g.
CH2 CH2CH3 CHSH
CH3
3-methy-1-butanethiol
13-27
Thiols/Disulfides: reactions
The thiol-disulfide redox pair is responsible for a critical factor in protein structure called a disulfide bridge.
H C
NH2
COOH
SH H C
NH2
CH2 S
COOH
HC
NH2
CH2S
COOH
cysteine, anamino acid
cystine, importantin proteins
I2 (very mild)
H2, PtLiAlH4
NaBH4
2
+ 2H
13-28
The End
Alcohols, etc.