Organic Compounds and
the Atomic Properties of
Carbon
1
10: Organic Compounds and the Atomic
Properties of Carbon
• 10.1 The Special Nature of Carbon and the Characteristics of
Organic Molecules
• 10.2 The Structures and Classes of Hydrocarbons
• 10.3 Some Important Classes of Organic Reactions
• 10.4 Common Functional Groups
2
Bonding Properties of Carbon
• Carbon forms covalent bonds in all its elemental forms and
compounds
• The ground state electron configuration of C is [He] 2s22p2; the
formation of carbon ions is therefore energetically unfavorable
• C has an electronegativity of 2.5, which is midway between that of
most metals and nonmetals → C prefers to share electrons
• Carbon exhibits catenation, the ability to bond to itself and
form stable chain, ring, and branched compounds
• Through orbital hybridization, C can form four bonds pointing in
different directions
• The small size of the C atom allows it to form short, strong bonds
• The short C-C bond allows the ready formation of π bonds, increasing
the variety of compounds that can be formed
3
The Position of Carbon in the Periodic Table
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
4
Comparison of Carbon and Silicon
• As atomic size increases down the group, bonds between
identical atoms become longer and weaker
• A C–C bond is much stronger than a Si–Si bond
• The bond energies of a C–C bond, a C–O bond, and a C–Cl bond
are very similar
• C compounds can undergo a variety of reactions and remain stable,
while Si compounds cannot
• Si has low energy d orbitals available for reaction, allowing Si
compounds to be more reactive than C compounds
5
Diversity and Reactivity of Organic Molecules
• Many organic compounds contain heteroatoms, atoms other
than C and H
• The most common of these are O, N, and the halogens
• Most reactions involve the interaction of an electron rich area
in one molecule with an electron poor site in another
• C–C bonds and C–H bonds tend to be unreactive
• Bonds between C and a heteroatom are usually polar, creating an
imbalance in electron density and providing a site for reactions to
occur
• A functional group is a specific combination of bonded atoms
that reacts in a characteristic way no matter what molecule it
occurs in
6
Heteroatoms and Bonding Arrangements
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
7
Carbon Skeletons
• Hydrocarbons are the simplest type of organic compound as
they contain only H and C atoms
• Each C atom can form a maximum of 4 bonds
• Single bonds can rotate relatively freely, so there are often
several different arrangements of a given carbon skeleton that
are equivalent:
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
8
Carbon Skeletons
Some five-carbon skeletons:
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
9
Drawing Carbon Skeletons
• Each C atom can form a maximum of four bonds
• These may be four single bonds
• or one double and two single bonds
• or one triple and one single bond
• The arrangement of C atoms determines the skeleton, so a
straight chain and a bent chain represent the same skeleton
• Groups joined by a single bond can rotate freely, so a branch
pointing down is the same as one pointing up
• A double bond restrict rotation, so different groups joined by a
double bond can result in different arrangements
10
Adding the H-atom Skin to the C-atom Skeleton
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
11
Naming Organic Compounds
• The name of any organic compound is comprised of three
portions:
PREFIX + ROOT + SUFFIX
• The root name of the compound is determined from the
number of C atoms in the longest continuous chain
• The suffix indicates the type of organic compound, and is
placed after the root
• Each prefix identifies a group attached to the main chain as
well as its position
12
Numerical Roots
Root
Number of C Atoms
meth-
1
eth-
2
prop-
3
but-
4
pent-
5
hex-
6
hept-
7
oct-
8
non-
9
dec-
10
13
Alkanes
• Hydrocarbons contain only C and H
• Alkanes are hydrocarbons that contain only single bonds and
are referred to as saturated hydrocarbons
• The general formula for an alkane is CnH2n+2, where n is any positive
integer
• Alkanes comprise a homologous series, a group of compounds
in which each member differs from the next by a –CH2– group
• The suffix for an alkane is –ane
14
Rules for Naming an Organic Compound
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
15
Depicting Organic Compounds
3-ethyl-2-methylhexane
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
16
Dispersion Forces and Physical Properties
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
17
Constitutional Isomers
• Constitutional or structural isomers have the same molecular
formula but a different arrangement of the bonded atoms
• A straight-chain alkane may have many branched structural
isomers
• Structural isomers are different compounds and have different
properties
• If the isomers contain the same functional groups, their properties will
still be similar
18
Constitutional Isomers: C4H10 and C5H12
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
19
Cycloalkanes
• Cycloalkanes are cyclic hydrocarbons → the C atoms of the
molecule are arranged in the form of a ring
• The general formula for a cycloalkane is CnH2n, where n is any positive
integer
• Cycloalkanes are saturated → all of the C atoms that make up
the ring are single bonded to other atoms (no double or triple
bonds)
• Cycloalkanes are nonplanar (except for three-carbon rings)
20
Depicting Cycloalkanes
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
21
Alkenes
• A hydrocarbon that contains at least one C=C bond is called an
alkene (or olefin)
• Alkenes are unsaturated and have the general formula CnH2n
• To name an alkene, the root name is determined by the
number of C atoms in the longest chain that also contains the
double bond
• The C chain is numbered from the end closest to the double bond
• The suffix for alkenes is –ene
22
Alkenes
23
Geometric Isomers
• The double bond of an alkene restricts rotation, so that the
relative positions of the atoms attached to the double bond
are fixed
• Alkenes may exist as geometric or cis-trans isomers
(stereoisomerism), which differ in the orientation of the groups
attached to the double bond
• Geometric isomers have different physical properties
24
Geometric Isomers: 2-Butene
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
25
Alkynes
• An alkyne is a hydrocarbon that contains at least one CΞC triple
bond
• Alkynes have the general formula CnH2n-2 and they are also
considered unsaturated carbons
• Alkynes are named in the same way as alkenes, using the suffix
–yne
26
Alkynes
27
Aromatic Hydrocarbons
• Benzene is an aromatic hydrocarbon and is a resonance hybrid
→ its  bond electrons are delocalized
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
28
Systematic Naming of Aromatic Compounds
• Systematic naming of aromatic compounds in which benzene is
the main structure: attached groups, or substituents, are named
as prefixes (however, many common names are still in use)
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
29
Types of Organic Reactions
• Addition reaction: when an unsaturated reactant becomes a
saturated product
• Elimination reaction: when a saturated reactant becomes an
unsaturated product
• Substitution reaction: when an atom or group from an added
reagent substitutes for one attached to a carbon in the organic
reagent
• Hydrolysis: a reaction in which a molecule of water breaks one or
more chemical bonds (can be an elimination, a substitution, …)
30
Addition Reaction
• An addition reaction occurs when an unsaturated reactant
becomes a saturated product
• The C=C, C≡C, and C=O bonds commonly undergo addition
reactions
• In each case, it is the  bond that breaks, leaving the σ bond intact
31
Addition Reaction
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
32
A Color Test for C═C Bonds
• Br2 (in pipet) reacts with a compound that has a C═C bond (in beaker), and
its orange-brown color disappears:
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
33
Elimination Reaction
• An elimination reaction occurs when a saturated reactant
becomes an unsaturated product
• This reaction is the reverse of addition
• The groups typically eliminated are H and a halogen atom or H
and an –OH group.
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
34
Elimination Reaction
• The driving force for an elimination reaction is the formation of
a small, stable molecule such as HCl (g) or H2O
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
35
Substitution Reaction
• A substitution reaction occurs when an atom or group from an
added reagent substitutes for one attached to a carbon in the
organic reagent
• The C atom at which substitution occurs may be saturated or
unsaturated, and X and Y can be many different atoms
(generally not C)
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
36
Aromatic Hydrocarbons
• Aromatic compounds are unusually stable → although they
contain double bonds they undergo substitution rather than
addition reactions
37
Functional Groups
• Organic compounds are classified according to their functional
groups, a group of atoms bonded in a particular way
• The functional groups in a compound determine both its
physical properties and its chemical reactivity
• Functional groups affect the polarity of a compound, and therefore
determine the intermolecular forces it exhibits
• Functional groups define the regions of high and low electron density
in a compound, thus determining its reactivity
38
Functional Groups in Organic Compounds
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
39
Functional Groups in Organic Compounds
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
40
Alcohols
• The alcohol functional group consists of a carbon bonded to an
–OH group (hydroxyl group)
• Alcohols are named by replacing the –e at the end of the
parent hydrocarbon name with the suffix –ol
• Alcohols have high melting and boiling points since they can
form hydrogen bonds between their molecules
41
Alcohols
• Alcohols can be classified based on which C atom is bonded to
the hydroxyl group
•
Primary alcohol: –OH bonded to a primary carbon atom (1°, bonded to
only one other carbon atom)
•
Secondary alcohol: –OH bonded to a secondary carbon atom (2°,
bonded to two other carbon atoms)
•
Tertiary alcohol: –OH bonded to a tertiary carbon atom (3°, bonded to
three other carbons)
42
Molecules with the Alcohol Functional Group
Phenol
Aromatic alcohol
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
43
Haloalkanes
• Haloalkanes or alkyl halides contain a halogen atom bonded to
carbon
• Haloalkanes are named by identifying the halogen with a prefix
on the hydrocarbon name (the C bearing the halogen must be
numbered)
2-Chloropropane
44
Amines
• The amine functional group contains a N atom
• The systematic name for an amine is formed by dropping the
final –e of the alkane and adding the suffix –amine
• Common names that use the name of the alkyl group followed
by the suffix –amine are also widely used
45
General Structures of Amines
• Amines are classified according to the number of R groups
directly attached to the N atom
• Primary (1°) amines are RNH2
• Secondary (2°) amines are R2NH
• Tertiary (3°) amines are R3N
methylpentylamine
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
46
Some Biomolecules with the Amine Group
Lysine (1°amine)
amino acid found in
proteins
Epinephrine (adrenaline; 2° amine)
neurotransmitter in brain;
hormone released during
stress
Adenine (1° amine)
component of nucleic
acids
Cocaine (3° amine)
brain stimulant; widely
abused drug
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
47
Properties of Amines
• Primary and secondary amines can form H bonds; they
therefore have higher melting and boiling points than
hydrocarbons or alkyl halides of similar mass
• Tertiary amines cannot form H bonds between their molecules
because they lack a polar N–H bond
• Amines of low molar mass are fishy smelling, water soluble,
and weakly basic
48
Aldehydes and Ketones
• Aldehydes and ketones both contain the carbonyl group, C=O
• Aldehydes are named by replacing the final –e of the alkane name
with the suffix –al
• Ketones have the suffix –one and the position of the carbonyl
must always be indicated
• Aldehydes and ketones are formed by the oxidation of alcohols
(primary alcohols for aldehydes, secondary alcohols for ketones) 49
Some Common Aldehydes and Ketones
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
50
The Polar Carbonyl Group
• The C=O bond is electron rich and is also highly polar
• It readily undergoes addition reactions, and the electron-poor
C atom attracts electron-rich groups
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
51
Carboxylic Acids
• Carboxylic acids contain the functional group –COOH (carboxyl
group)
• Carboxylic acids are named by replacing the –e of the alkane
with the suffix –oic acid
• Carboxylic acids are weak acids in water, and react with strong
bases:
52
Some Molecules with the Carboxylic Acid Group
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
53
Esters
• The ester group is formed by the reaction of an alcohol and a
carboxylic acid
• The first part of the ester name designates the alcohol portion and
the second the acid portion: the -ic ending of the parent acid is
replaced by the suffix -ate
• Example: ethyl ethanoate (ethyl acetate), ester formed between
ethanol and ethanoic acid
• Ester groups occur commonly in lipids, which are formed by the
esterification of fatty acids
• Ester hydrolysis can be carried out using either aqueous acid or
aqueous base → when base is used the process is called
saponification
54
Amides
• An amide contains the functional group:
• Amides, like esters, can be hydrolyzed to give a carboxylic acid
and an amine
• The peptide bond, which links amino acids in a protein, is an
amide group
55
Some Molecules with the Amide Group
Copyright ©McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
56
Functional Groups with Triple Bonds
• Alkynes contain the electron rich –CΞC– group, which readily
undergoes addition reactions:
• Nitriles contain the group –CΞN and are made by a substitution
reaction of an alkyl halide with CN- (cyanide):
57
Sample Problem 2
Recognizing Functional Groups
• PROBLEM: Circle and name the functional groups in the
following molecules:
58
Sample Problem 3
Nomenclature of Organic Compounds
• PROBLEM: Name the following compounds:
a)
c)
b)
d)
59
Polymers
• Polymer: any of a class of natural or synthetic substances
composed of very large molecules (macromolecules), that are
formed by repeating units
• Monomer: a molecule that can react with other molecules to
form very large molecules, or polymers
• Addition polymers, also called chain-growth polymers form
when monomers undergo an addition reaction with each
other
• The monomers of most addition polymers contain an alkene group
• Condensation polymers are formed when monomers link by a
dehydration-condensation type reaction
• The monomers of condensation polymers have two functional groups,
and each monomer can link to two others
60