Ch. 3 Review: Nomenclature: Organic Compounds Compounds of carbon--organic chemistry –If they have...
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Transcript of Ch. 3 Review: Nomenclature: Organic Compounds Compounds of carbon--organic chemistry –If they have...
Ch. 3 Review: Nomenclature: Organic Compounds
• Compounds of carbon--organic chemistry– If they have only C and H, hydrocarbons
– e.g. alkanes: methane CH4, ethane C2H6, propane C3H8
• general formula: CnH2n+2
– Know Table 3.7
• Functional Groups– R = hydrocarbon group
– e.g. alcohols: methanol CH3OH, ethanol C2H5OH
– e.g. amines: propyl amine, butylamine– Know functional groups in Table 3.8
Methanol (wood alcohol), CH3OH, is related to methane, CH4, by replacing one H with OH.
Organic chemistry -- Chapter 20
• Introductory Topics
Bonding & Structure -- Review Chapters 3, 9, and 10!!Types of Chemical Formulase.g. 2-propanol (iso-propanol)
!!! Always FOUR BONDS to Carbon !!!
H C
H
H
C
O
H
C
H
H
H
H
expandedstructuralformula
H3C CH
OH
CH3
orOH
CH3CHCH3
condensed structural formula
OH
fully condensedstructural formula
(missing C’s and H’s are understood)
“line drawing”
Isomerism• Isomers– different molecules with the same molecular
formulaStructural isomers--different pattern of atom attachment; different connectivity
Stereoisomers—same atom attachments (connectivity), different spatial orientation
Rotation about a single bond is not isomerism!!
Structural Isomers• Structural Isomers -- same chemical formula, but
different arrangement (connectivity) of atomse.g. C3H8O - 3 isomers (2 alcohols, 1 ether)
Number of possible isomers can be very large, e.g.
C3H8 C4H10 C5H12 C6H14 C8H18 C10H22 C20H42
1 2 3 5 18 75 > 105
CH3 CH2 CH2 OH
H3C CH
OH
CH31-propanol2-propanol
ethyl methyl ether
CH3 CH2 O CH3
Stereoisomers• Stereoisomers—same atom attachments (connectivity),
different spatial orientation• Optical isomers (enantiomers)—are molecules that
are nonsuperimposable mirror images of each other
• Geometric isomers—are stereoisomers that are not optical isomers, e.g. cis and trans
Chiral Molecules• Are molecules that have nonsuperimposable mirror
images– If 4 different groups are attached to carbon, it will be
chiral– Chiral molecules will rotate plane-polarized light– Most physical properties are identical, but in a chiral
environment enantiomers behave differently
7
Isomerism; Overview
Many Possible CompoundsA Tremendous Variety of organic molecular structures and
properties are possible, e.g.:
H
C
H
C
H
Cl
C
H
H
C
H
Cl n
CH3 C
O
OH
COH
O
O C
O
CH3
vinyl chloride poly(vinyl chloride) “PVC”
acetic acid
aspirin
More Organic Compounds
N
O
CH3
O
CH3
N
N
CH3
CH3 N
H
H
CaffeineC8H10N4O2
methylamine
fortunately, the subject is very systematic !and is readily classified by “organic functional groups”
Hydrocarbons• Alkanes CnH2n+2
CH4 methane C5H12 pentane
C2H6 ethane C6H14 hexane
C3H8 propane C7H16 heptane
C4H10 butane C8H18 octane, etc….
alkyl groups:
methyl CH3
ethyl CH3CH2
phenyl C6H5
H C
H
H
H C
H
H
C
H
H
Alkane Nomenclature1. Name parent chain--longest continuous chain2. Number parent chain
-- First branch gets lowest possible number
3. Name & number branches4. Order branches
-- Alphabetical order-- Multiple identical substituents get prefix
CH3CH2CHCHCHCH2CHCH3
CH3 CH3 CH3
CH2CH3
5-ethyl-2,4,6-trimethyloctane
C N
Br
5-bromo-2-cyano-4-methylheptane
Samples:
(see book for detailed “rules” and other functional groups)
Reactions of Alkanes (generally unreactive)
• Combustion -- fuels!e.g. C5H12(l) + 8 O2(g) --> 5 CO2(g) + 6 H2O(l)
• Free radical substitution (not selective!) C2H6(g) + Cl2(g) --> C2H5Cl(g) + HCl(g)
• Dehydrogenation (reverse rxn is more common!) C2H6(g) --> H2C=CH2(g) + H2(g)
• “Cracking” of hydrocarbons (petroleum industry)
needs heat!
needs heat and/or pressure!
needs heat!needs catalyst!
Alkenes ~ C=C double bond
CnH2n (with one double bond)
• Geometric isomers are possible, e.g.:
– Restricted C=C bond rotation– Trigonal planar geometry at C=C carbons– sp2 hybridization at C=C carbons
• Nomenclature (C=C bond takes preference)
H3C
C
H
C
CH3
H
H
C
H3C
C
CH3
H
cis-2-butene trans-2-butene
CH3CH2CHCH2CH=CCH3
CH3 CH3
2,5-dimethyl-2-heptene cyclohexene
Reactions of Alkenes
addition to double bond
RCH=CH2 + HX --> RXCH-CH3
R
C
H
C
H
H
H X
R
C
H
C
H
H
HX
R
C
H
C
H
H
HX
X
RHC CH3
+
≡
Markovnikov’s rule ~ “them that has, gets”(H goes on the C that already has the most H’s)
Addition of non-polar reagents (H2, Br2, etc) also occurs
Alkynes ~ C≡C Triple Bond
CnH2n-2 (with one triple bond)
• linear geometry at C≡C carbons• sp hybridization at C≡C carbons• no “cis-trans” isomers• similar addition reactions to alkenes
(stepwise addition can occur)
R C C H
X
C
R
C
Y
H
X
C
X
C
Y
Y
HRXY XY
Aromatic Hydrocarbons(benzene and its derivatives)
Benzene ~ C6H6
• planar 6-membered ring (especially stable)• all C-C distances equivalent• sp2 hydridization at all carbons• delocalized set of 3 double bonds (6 electrons)
other common aromatic hydrocarbons:
napthalene anthracenes
Aromatic Nomenclature• Aromatic ring as substituent
– Phenyl (C6H5–)
– Benzyl (C6H5CH2–)
• Monosubstituted benzene– (name of substituent)benzene– Some common “trivial” names
• Toluene• Phenol
• Polysubstituted benzene– Assign numbers to substituents
H2C CH CH2 CH2 CH3CH
4-phenyl-1-hexene
CH2CH2CH3
propylbenzene
F
Br1
23
1-bromo-3-fluorobenzene
Aromatic Substitution Rxns• Substitution Reactions of Aromatic Hydrocarbons (never
addition!)
H
H
X
X
H
H
X
H
NO2
H
X2
X2
X = Cl, Br
HNO3
(H+ catalyst)
( NOT aromatic! )
needs catalyst!
Organic Functional Groups
Family Characteristic Structural Feature
Examples
Hydrocarbons alkanes alkenes alkynes aromatic
only single bondsC=CC≡C
benzene ring
CH3CH3
CH2=CH2
HC≡CH
Alcohols* R-O-H CH3CH2OH
Ethers* R-O-R’ CH3OCH3
* structures like waterH
O
H
More Organic Functional Groups
Family Characteristic Structural Feature
Examples
Aldehydes
Ketones
Carboxylic Acids
Esters
“carbonyl” compounds
R C
O
H
R C
O
R'
R C
O
OH
R C
O
OR'
H3C C
O
H
H3C C
O
CH3
H3C C
O
OH
H3C C
O
OCH3
C
O
More Organic Functional Groups
Family Characteristic Structural Feature
Examples
Amines: 1º 2º 3º
RNH2
RNHR’RNR’R”
CH3NH2
(CH3)2NH
(CH3)3N
Amides R C
O
N
H (R')
H (R")H3C C
O
NH2
N
Alcohols (organic derivatives of H2O)
NomenclatureAlcohols, R-O-H
R = CH3 methanol
R = CH3CH2 ethanol
R = CH3CH2CH2 1-propanol (n-propanol)
CH3CHCH3
OH
2-propanol(iso-propanol)
OH
3,7-dimethyl-4-octanol
OH
phenol
Reactions of AlcoholsOxidation
H
CR
H
O H
H
CR
R
O H
R
CR
R
O H
R C
O
H
R C
O
R
primary
[O]
– “H2”aldehyde
secondary
[O]
– “H2”ketone
[O]No Reaction
[O] = oxidizing agent, e.g. Cr2O72–
tertiary
More Reactions of Alcohols
R C
H
CH2
OH
H
R
C
H
CH2
Elimination
alcohol
H+
alkene
+ H2O
Substitution
RCH2—OH + H—X – H2O
RCH2—Xalcohol
X = Cl, Br, Ialkyl halide
Aldehydes and Ketones
Nomenclature
H C
O
H H3C C
O
H CH3CH2 C
O
H
H3C C
O
CH3 H3C C
O
CH2CH3
O
methanal(formaldehyde)
ethanal(acetaldehyde)
propanal
propanone(acetone)
butanone(methyl ethyl ketone) 5-methyl-3-heptanone
Reactions of Aldehydes and Ketones
Hydrogenation (reduction) of aldehydes and ketones
R C
O
H
R C
O
R'
R C
O
OH
R C
OH
H
H
R C
OH
R'
H
R C
O
H
aldehyde
“H2”
primary alcohol
ketone
“H2”
secondary alcohol
Oxidation of aldehydes (very easy!)
aldehyde
[O]
carboxylic acid
Carboxylic AcidsNomenclature of Acids
H C
O
OH H3C C
O
OH C
O
OH
CH3CH2CH2 C
O
OH
H3C C
O
OH H3C C
O
ONa
methanoic acid(formic acid)
ethanoic acid(acetic acid) benzoic acid
butanoic acid
CH3CH2CH2CO2H(condensed formula)
Salts of Acids
acetic acid
NaOH
H2O
sodium acetate
Condensation Reactions
• a condensation reaction is any organic reaction driven by the removal of a small molecule, like water
• esters are made by the condensation reaction between a carboxylic acid and an alcohol
the reaction is acid catalyzed
• acid anhydrides are made by the condensation reaction between 2 carboxylic acid molecules
the reaction is driven by heat
R C
O
OH OH C
O
R' R C
O
O C
O
R'
+ + HOH
Esters
Nomenclature of Esters
R C
O
O R' H3C C
O
O CH2CH3
CH3CH2CH2 C
O
O CH2CH3 C
O
O CH3
H O R'
O
CR O H R C
O
O R'
alkyl group
acid name
-ateethyl acetate
ethyl butanoatemethyl benzoate
Formation of Esters (from acid + alcohol)
+ + H2O
EthersEthers R – O – R’
CH3CH2–O–CH2CH3 diethyl ether
CH3–O–CH2CH2CH3 methyl propyl ether
• Ether Synthesis:
R–O–H + H–O–R R–O–R
H+
– H2O
Amines(organic derivatives of NH3)
H3C N H
H
H3C N H
CH3
H3C N H
CH2CH2CH3
NH2
NH2
methylamine dimethylamine methylpropylamine
2-aminohexane aniline
Like ammonia, amines are weak bases:
RNH2 + H+ RNH3+
Amides
Acid derivatives (e.g. 1º amides: –NH2 instead of –OH)
O
CR O H H NH2R C
O
NH
H+ + H2O
Nomenclature
R = CH3
R = CH2CH2CH2CH3
ethanamide
pentanamide, etc.
amides (unlike amines) are generally not basic (due to e- withdrawing effect of the C=O group)
Sample Questions
(1) Write complete, systematic names for:
H3C C CH CH CH3
CH2CH2H3C C N
C
O
O CH
CH3
H2C CH3
H C
O
CH2 CH2 CH CH2 CH3
Sample Questions, cont.(2) Write complete, specific structural formulas for all of the
organic reactants and products in the reaction.
an ester sodium acetate + 3-pentanol
(3) Show, with specific structures and reactions, how the following compound can be prepared in three steps starting with the appropriate alkyne.
NaOH
H3C C
O
CH
CH3
CH3
Answers1. 2-cyano-4-methyl-3-heptene 2-butylbenzoate 4-phenylhexanal2.
H3CC
O
O
CH
CH2
CH2
CH3
CH3 H3CC
O
ONa+ OH
H C C CH
CH3
CH3
H
C
H
C
H
CH CH3
CH3
H
C
H
C
H
CH CH3
CH3
H C
H
H
C
OH
H
CH
CH3
CH3
NaOH+
3.+ H2
cat,
pressurestep 1
+ H2O acid catstep 2
Answers, cont.
3., cont.
H C
H
H
C
OH
H
CH
CH3
CH3
[ox]H3C
C
O
CHCH3
CH3
Organic Polymers
Polymers -- macromolecules made up of many repeating units called monomerse.g. polystyrene is formed via the polymerization of the monomer styrene:
e.g. some rings can open to form polymers:
HC CH2 CH CH2 n
O CH2 CH2 CH2 CH2 On
h
styrene polystyrene
n ~ 103 - 106
Methods of PolymerizationAddition (very common -- works with most alkenes)
CH2=CH2 + CH2=CH2 + CH2=CH2 etc….
---CH2–CH2–CH2–CH2–CH2–CH2--- =
• requires an initiator (e.g. a catalyst or UV light) to start the “chain” reaction
CH2n
More Methods of PolymerizationCondensation (common for polyesters and polyamides)
a small molecule (e.g. H2O) byproduct is formed
X-A-Y + X-B-Y Ring-Opening (uncommon except for polyethers and
most inorganic polymers, e.g. silicones)
A Bn
A B A B A B A
– XY
A B
etc…
Common Addition PolymersMonomer Polymer
CH2=CH2—CH2–CH2—n
ethylene polyethylene
CH=CH2
styrene
—CH–CH2—n
polystyrene
CH=CH2
Cl vinyl chloride
—CH–CH2—n
—CH–CH2—n
Clpoly(vinyl chloride) ~ PVC
CH=CH2
N≡C N≡Ccyanoethene “Orlon”
One More Common Addition Polymer!
Addition polymerization of dienes
H2C C
CH3
CH CH2CH2 C
CH3
CH CH2n
“isoprene”(2-methyl-1,3-butadiene)
“natural” rubber
Common Condensation Polymers
Polyesters
C
O
C
O
O CH2 CH2 O
n
H O C
O
A C
O
O H H O B O H
C
O
A C
O
O B On
A B CH2 CH2
+diacid diol
polyester
– H2O
e. g. = =
“Dacron”
Sample QuestionWrite a complete structural formula of the organic polymer
that is produced in each reaction. State whether the polymerization process is addition, condensation, or ring-opening.
CHO
O
COH
O
O
CH3
CH2 CH
C N
+ HO-CH2CH2-OH
Answer
a. condensation
b. ring-opening
c. addition
d. addition
O
n
CH2 CH
C N
n
n
O
O O
O CH2CH2
n