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ORGANIC CHEMISTRY
Chapter 20
Organic
• Comes from the word “organism”
• Originally thought that carbon compounds
could only be synthesized by living organisms
• Not so – German scientist synthesized urea – a
carbon compound found in urine in 1828
Carbon Bonding
• Because carbon bonds readily with H, N, O, S,
and halogens, as well as itself, there are
millions of carbon compounds.
• Carbon compounds are considered organic
EXCEPT for
– carbon dioxide,
– carbides, and
– carbonates.
Hydrocarbons
• Simplest organic compounds
• Contain only hydrogen and carbon in long
strings or chains
• Their carbon-carbon covalent bonds are single
• Saturated – has the maximum number of
hydrogens - alkanes
When a carbon atom has 4 atoms bound to it,
these atoms form a tetrahedral shape.
Representing Alkanes
• Chemical formulas - generic alkane formula is
CnH2n+2, ex. CH4, C2H6, C3H__
• Structural formulas – show all C’s and H’s
• Condensed structural formulas – C’s with # of
H’s attached. ex. CH3 CH2 CH2 CH3
• If there is more than one way to correctly
represent an alkane it has structural
isomerism – the different structures are called
isomers
Naming Straight Chain Alkanes
all carbon – carbon bonds are single bonds
• Count the number of
carbons and use
appropriate prefix with
“ane” ending.
• meth -1,
• eth -2,
• prop - 3,
• but - 4,
• pent- 5,
• hex - 6,
• hept - 7,
•
•
•
•
•
•
•
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oct- 8,
non - 9,
dec- 10
Ex. Name CH4
1 carbon, so methane
Name C2H6
2 carbons, so ethane
Alkanes: see table 20.1 on
page 704
Alkenes
have a double carbon-carbon bond
• generic alkene formula is CnH2n
• Unsaturated – because of the double bond,
has less than maximum number of hydrogens
• Count the number of carbons and use
appropriate prefix with “ene” ending.
• As necessary, number the carbons so as to
identify the location of the double bond on
the lowest numbered carbon.
Alkynes
have a triple carbon-carbon bond
• generic alkyne formula is CnH2n-2
• Unsaturated – because of the triple bond, has
less than maximum number of hydrogens
• Count the number of carbons and use
appropriate prefix with “yne” ending.
• As necessary, number the carbons so as to
identify the location of the triple bond on the
lowest numbered carbon.
• Not common in nature
Substituent groups
• A group that is substituted for a hydrogen
• Named by the number of carbons in the group
with a “yl” ending
• Ex. If a hydrogen is replaced by a CH3 it is a
methyl substituent.
• What would the substituent be if CH2CH3
replaced a hydrogen?
• See table 20.2 on page 709
Naming Alkanes with Substituent(s) page 710
(aka as branched chains)
• Find the longest continuous chain of carbon
atoms (may not be “straight”) – this is the
parent chain and determines the base alkane
name
• Number the carbons in the chain so that the
substituent group (alkyl group – carbon(s) and
hydrogen) is on the lowest # carbon
• Using the appropriate name for each alkyl
group, identify its place on the parent chain
with a number.
Naming Alkanes with Substituent(s) con’t
• When a given type of alkyl group occurs more
than once, attach the appropriate prefix (di,
tri, etc.) to the alkyl name.
• If there is more than one type of alkyl group,
they are listed in alphabetical order,
disregarding any prefix.
• Commas separate numbers.
• Dashes separate numbers from letters.
Substituent groups with alkenes and
alkynes
• Same as alkanes with 2 differences
• 1. parent chain is always the longest chain
containing the double or triple bond (even
though it may not be the longest possible
chain)
• 2. position of double or triple bond (not
branches) determines how the chain is
numbered
Homework
• Practice Problem 20.1 page 703
• practice 20.4 (page 711)
and 20.5 (page 714)
• Page 717, #1,3,4, (#4 name them too), 6, 8
• Page 719 practice problem 20.6
Functional Groups
• Table 20.6 page 727
• An atom or group of atoms in a hydrocarbon
derivative that contains elements in addition
to carbon and hydrogen.
Halocarbons
• A halogen replaces one of the hydrogens in a
carbon chain.
• If necessary, number the carbons and identify
the location of the halogen(s)
• Ex. chloromethane
• 1,2-dichloromethane
• 1,1-dichloromethane
Alcohols
• Most common
• Have -OH group on carbon chain replacing a
hydrogen
Aldehydes and Ketones
• Aldehydes have a carbonyl group (C=O) at the
end of a carbon chain
• To name, replace final “e” of parent chain with
“al” Will always be on # 1 carbon Ex. ethanal
• Ketones have a carbonyl group (C=O) in the
midst of a carbon chain
• To name, number carbons so that carbon in
carbonyl group has smallest number, then
replace final “e” of parent chain with “one”.
Identify position of carbonyl group with #. Ex.
2-pentanone
Carboxylic acids
• Have a carboxyl group (-COOH (one of the
oxygens is doubled bonded to the carbon))
• Name by dropping the final “e” on the parent
chain (longest chain with COOH group) and
adding “oic acid”
• Ex. HCOOH methanoic acid
type
Alkanes
Alkenes
Alkynes
Substituent groups
Halocarbons
Alcohols
Aldehydes
Ketones
Carboxylic acids
Special feature
Naming
HW – due Thursday 5/13
• P. 735 #20.9
• P 741 #2
• P 746 #48, 49, 50 a-d; 51 b,c,e; 54 a,d; 55 a,d,e