Intro to organic chemistry ( orgo )
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Transcript of Intro to organic chemistry ( orgo )
Intro to organic chemistry (orgo)SCH4U – Unit B
Organic Compounds•Organic chemistry: chemistry of carbon
compounds▫Exceptions are oxides of carbon (CO2 and
CO), carbonates, bicarbonates, and cyanides
•Carbon atoms are generally bonded to:▫Each other▫Hydrogen atoms▫Other specific elements (O, N, S, P and
others)
Why study organic chemistry?1. Life is carbon-based. Everyone is made
up of organic compounds. There are more known carbon compounds than any other element.
2. There are several million known organic compounds with ~30,000 more being “discovered” each year.
3. Some common organic compounds include plastics, synthetic and natural fibres, dyes, drugs, pesticides, lighter fluid, and gasoline.
The carbon atom•Carbon has four valence electrons
allowing it to form four bonds with other atoms by sharing its electrons▫This results in a tetrahedral shape
•Carbon forms covalent bonds (sharing of electrons) with carbon atoms
Classification•Since organic compounds are composed
almost entirely of carbon, they are sometimes referred to as hydrocarbons
•Hydrocarbons can be divided into:1. Aliphatics: carbon atoms in an open chain
structure; may have branches, but no rings
2. Alicyclics: carbon atoms arranged in a ring structure
3. Aromatics: structures related to benzene (C6H6)
Classification•Aliphatics can be further categorized into:
1. Alkanes: contains only single bonds (saturated)
2. Alkenes: contains at least one double bond (unsaturated)
3. Alkynes: contains at least on triple bond
IsomersIsomers
Constitutional Isomers
Stereoisomers
Diastereomers Enantiomers
IsomersConstitutional Isomers Stereoisomers
Isomers have same molecular formula
Isomers have same molecular formula
Atoms bonded in a different sequence
Atoms bonded in same sequence
Also known as structural isomers
Differ in 3D orientation of atoms in space
IsomersDiastereomers Enantiomers
Based on a double bond Mirror images of each other around a single carbon atom
Carbon atoms with different types of atoms
At least one carbon atom bonded to four different types of atoms or groups
cis isomer when two identical groups or atoms are on the same sidetrans isomer when two identical groups or atoms are on the opposite side
Diagrams & formulas•A number of different (but related)
diagrams used to express structures in organic chemistry:▫Empirical molecular formula▫Expanded molecular formula▫Complete structural formula▫Condensed structural formula▫Line structural formula▫3D structural formula
Alkanes# of carbons Prefix # of carbons Prefix
1 Meth- 6 Hex-
2 Eth- 7 Hept-
3 Prop- 8 Oct-
4 But- 9 Non-
5 Pent- 10 Dec-
Alkanes•Only single bonds present in the main
chain•General formula is CnH2n+2
•Form a tetrahedral shape▫Note: more on shapes in the next unit
•Create a 109.5° angle between bonds•Considered “saturated” because no other
hydrogen atoms can be added•Always end in “~ane”
Nomenclature•Three parts to organic chemistry
nomenclature:▫Prefix: indicates number, type and location
of branches and/or functional groups (if any)
▫Root: indicates the number of carbon atoms in the main (parent) chain
▫Suffix: indicates the number and location of double or triple bonds (if any) and/or highest priority functional group
Let’s draw alkanes!•Draw all ten basic alkanes and name
them.
Alkyl groups and branching•Each branch of a hydrocarbon is referred
to as an alkyl group (if it contains only C and H)
•Alkyl groups use the same basic roots as alkanes
•Alkyls always end in “~yl”•Also contain a number and hyphen in
front to indicate location on the main carbon chain▫Example: 2-methyl pentane
CH3
CH2CH2
CHCH3
CH3
Alkyl groups and branching•Find the longest carbon chain and assign
sequential numbers to each carbon▫Assign these numbers temporarily starting
from both ends of the carbon chain▫Ultimately will select only one set of
numbers to use•The goal is to use the numbering along
the carbon chain that gives the lowest values assigned to branches
Alkyl groups and branching•Let’s try some! Draw 3-ethyl octane…
CH3 CH2
CH CH2
CH2 CH2
CH2 CH3
CH2CH3
Alkyl groups and branching
Alkyl groups and branching•When there is more than one branch, they
are listed in front of the root and suffix according to alphabetical order of the name of the alkyl group
•Try naming…
•4-ethyl 3-methyl heptaneCH3CH2
CH2CH
CH
CH3
CH2
CH3
CH2CH3
Alkyl groups and branching•If there is more than one of any given
alkyl group▫Indicate all the number for the positions
using commas to separate the numbers, and
▫Use prefixes (on the prefixes – confused yet?) to indicate the number present
Alkyl groups and branching•Try naming…
•5,6-diethyl-3,3,4-trimethyl nonane
CH3
CH2CH2
CH
CH
CH
C
CH2
CH3
CH3
CH3
CH3CH2CH3
CH2
CH3
Alkenes•At least one double bond present in the
main chain•General formula is CnH2n
•Form a trigonal planar shape▫Note: more on shapes in the next unit
•Create a 120° angle between bonds•Considered “unsaturated” because other
hydrogen atoms can be added•Always end in “~ene”
Nomenclature1. Identify and name the longest carbon chain
that CONTAINS THE DOUBLE BOND(S).2. Number the carbons in the chain so that the
two carbons involved in the double bond have the lowest possible numbers.
a) If the double bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number.
3. Follow same rules for identifying and naming prefixes.
Nomenclature•Try naming this…
•2-ethyl 1-pentene
CH3 CH2
CH2 C
CH2 CH3
CH2
Nomenclature•Now let’s draw 1-butene and 2-butene…
1-butene 2-butene
CH3
CH2 CH
CH2
CH3
CH CH
CH3
Nomenclature•Let’s try a structure with more than one
double bond…
1,3-pentadiene
CH3
CH CH
CH CH2
Nomenclature•Let’s put everything together and name…
•4-ethyl-3,6-dimethyl 1,2,4-octatrieneCH3
CH3
CH3
CH2
CH
CH
C
C
C
CH2
CH2
CH3
Diastereomers•Consider the following compounds…
cis-2-butene trans-2-butene 2-methyl-1-propene
CH3
CH CH
CH3CH3
CH CH
CH3 CH3
C
CH3 CH2
Diastereomers•Not superimposable upon one another•Result from lack of free rotation around
the double bond•Priorities are assigned to the two groups
attached to the carbon atoms on either side of the double bond (starting with the carbon to the left of the double bond) based on atomic number▫Largest atomic number at the first
point of difference has the highest priority
Diastereomers•If two highest priority groups are on the
same side of the double bond (top or bottom)…▫cis configuration
•If two highest priority groups are on the opposite side of the double bond…▫trans configuration
Alkynes•At least one triple bond present in the
main chain•General formula is CnH2n-2
•Form a linear shape▫Note: more on shapes in the next unit
•Create a 180° angle between bonds•Considered “unsaturated” because other
hydrogen atoms can be added•Always end in “~yne”
Nomenclature1. Identify and name the longest carbon chain
that CONTAINS THE TRIPLE BOND(S).2. Number the carbons in the chain so that the
two carbons involved in the triple bond have the lowest possible numbers.
a) If the triple bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number.
3. Follow same rules for identifying and naming prefixes.
Nomenclature•Try naming this…
•3,4-dimethyl 1-hexyne
CH C CH
CH CH2
CH3
CH3 CH3
Nomenclature•Now let’s draw 1-butyne and 2-butyne…
1-butyne 2-butene
CH3
CH2
C
CH
CH3 C C CH3
Nomenclature•Let’s try a structure with more than one
triple bond…
2,4-hexadiyne
CH3 C C C C CH3
Nomenclature•Let’s put everything together and name…
•4-ethyl-4,5-dimethyl 2,6-octadiyne
CH3 CH2
CH3
C
C
C
CH
C
C
CH3CH3
CH3
Alicyclics•Connected end-to-end forming a ring•Have single and/or double bonds present
in the main chain•General formula is CnH2n
•Can be “saturated” or “unsaturated”•Suffix changes depending on presence of
double bonds•Prefix used is always “cyclo~” before the
root
Nomenclature•Try naming…
cyclobutane cyclo-1-pentenecyclopent-1-ene
CH2
CH2 CH2
CH2
CH
CH2
CH2
CH2CH
Nomenclature•Try drawing…
cyclo-1,4-hexadiene 2,7-diethyl-4-methylcyclo-1,3,5-
heptatriene
CH
CH2 CH
CH
CH2CH
CH3
CH2
CH3CH
C CH
C
CH
CH
CH
CH2
CH3
Aromatics•Based on benzene and the presence of
benzene-like rings•Benzene is a six-carbon ring with three
double bonds▫Cyclo-1,3,5-hexatriene
•However, the electrons in the double bonds are actually spread over the whole molecule = delocalized▫Benzene actually has six identical “1 ½”
bonds
Aromatics•Creates greater stability in the molecule•These “1 ½” bonds do not behave/react
like double bonds•Molecules that have this type of sharing
are referred to as aromatic compounds
Benzene CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
Aromatics•Some common aromatics…
benzene napthalene
antracene
CH
CH
CH
CH
CH
CHCH
CH
CH
C
C
CH CH
CH
CH
CH
CH
CH
CH
C
C
CH CH
C
C
CH CH
CH
CH
CH
Nomenclature1. Number carbons in benzene ring assigning
lowest number to a branch.a. If more than one branch exists, start numbering
at the branch that contains the group with the highest priority (most complex).
2. Name branches attached to the benzene ring, assigning numbers to each branch.
a. If only one branch is present, a number does not need to be assigned.
3. Branches are placed before the root as a prefix.
Nomenclature•Priority of branches on benzene…
Highest priority -OH-NH2-F, -Cl, -Br, -I-CH2CH2CH3-CH2CH3
Lowest priority -CH3
Nomenclature•When benzene has only two branches,
position numbers do not have to be used•Instead, prefixes ortho-, meta-, and para-
replace position numbers
1,2-dimethyl benzeneortho-dimethyl benzene
CH3
CH3
C
CH
CH
CH
CH
C
Nomenclature
1,3-dimethyl benzene1,4-dimethyl benzenemeta-dimethyl benzene para-dimethyl benzene
CH3
CH3
CH
C
CH
CH
CH
C
CH3
CH3
CH
CH
C
CH
CH
C
Nomenclature• IUPAC has retained many of the common names for
aromatics…
Nomenclature•Let’s try naming…
3-ethyl-5-methyl phenol
CH3
OH
CH3CH2
C
CH C
CH
CCH
Nomenclature•Let’s try drawing…
2,6-diethyl-3-methyl benzaldehyde
CH3
OCH
C
C C
C
CHCH
CH2CH3
CH2
CH3
Nomenclature•For use when:
▫Naming compounds with >1 fxn’l group▫Naming compounds with a complicated
substituent
Nomenclature•Try naming…
3-phenyl hexane
CH3
CH2 CH2
CH CH2
CH3C
CH
CHCH
CH
CH
Nomenclature•Try drawing…
4,6-diphenyl 2-octene
C
CH3CH
CH
CH
CH2CH
CH2CH3 CH
CH
CH
CH
CH
C
CH
CH
CH
CH
CH
Up next•That covers the basics of hydrocarbons in
organic chemistry.•Next we will cover functional groups!