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Introduction to Organic Chemistry
NomenclatureWriting form: Prefix – parent – locant – SuffixSteps:1. Parent hydrocarbon2. Number the atoms in main chain3. Identify and number substituents4. Write the name as a single word5. (cycloalkane– chair conformation)
Number of “C” atoms Word root
1 meth
2 Eth
3 Prop
4 But
5 Pent
6 Hex
7 Hept
8 Oct
9 Non
10 Dec
Functional Group Representation
Alkane C-C single bond
Alkene C-C double bond
Alkyne C-C triple bond
Carboxylic acid -COOH
Alcohol -OH
Nomenclature
13 24
13 24
2, 3-dimethybutane
Questions:
Cyclobutane
1-bromo-1-chlorobutane
2,2-dimethylpentane
1,1- dimethylcyclopentane
1,4-dimethylcyclohexane
Lines• Bonds to atoms above the plane of the drawing
(coming out, toward the viewer) are shown with a bold wedge ( ), with the narrow end of the wedge starting at the stereogenic center.
• Bonds to atoms below the plane (going in, away from the viewer) are shown with hash wedges ( ).
Sawhorse representation and Newman projection
Sawhorse representation Newman Projection
Views C-C bond from an oblique angle Views C-C bond directly end-on
Indicated spatial relationships by showing all the C-H bonds
Carbon atoms are represented by a circle
Available: http://image.wistatutor.com/content/hydrocarbons/newman-projections.gif
Staggered and eclipsed
Sawhorse projection
Newman projection
Stability
Skeletal structures
Cyclohexane
Propene
Benzene
Benzene and phenyl• The benzene ring• All aromatic compounds are based on benzene, C6H6, which has a ring of
six carbon atoms and has the symbol:• Each corner of the hexagon has a carbon atom with a hydrogen attached.
• The phenyl group• A hydrogen is removed from a benzene ring, C6H6. Like a methyl or an
ethyl group, a phenyl group is always attached to something else (not carbon).
Benzene-1,4-dicarboxylic acid
2-hydroxybenzoic acid
2,4,6-trichlorophenol
Functional group
• A group of atoms whose bonding is the same from molecule to molecule.
• Imparts similar chemical and physical properties to the molecules which contain them.
Imine Functional Group
Also called Schiff Base=NH
Imine
• Carbon–nitrogen double bond• Nitrogen attached to a hydrogen atom (H) or
an organic group.• The carbon has two additional single bonds
Examples of Imines
Rhodopsin, an imine used in vision.(E)-N-Benzylidenemethanamin
• Related to ketones and aldehydes by replacement of the oxygen with an NR group
• When R = H, the compound is a primary imine • When R is hydrocarbyl, the compound is a
secondary imine
Imines
R2C=NR'
• When R3 is OH, the imine is called an oxime
• When R3 is NH2 the imine is called a hydrazone
Aldimines and ketimines• A primary imine in which C is attached to both
a hydrocarbyl and H is called a primary aldimine
• A secondary imine with such group is called a secondary aldimine
• A primary imine in which C is attached to two hydrocarbyls is called a primary ketimine
• A such group is called a secondary ketimine.
Naming Imines
• Imines are systematically named by adding the word imine after the name of the corresponding aldehyde or ketone
• CH3CHNH
• ethanal imine (from ethanal, CH3CHO) • Btw, is this a primary/secondary
aldimine/ketamine?
Naming Imines
• (CH3)2CNH• Propanone imine • Ethanal methyl imine• CH3CHNCH3
Nitrile
–C≡N
Nitriles
• any organic compound that has a –C≡N functional group
• Inorganic compounds containing the -C≡N group are not called nitriles, but cyanides
Naming Nitriles
• 2 ways of naming nitriles
Cyano substituent style
- The root name is based on the longest chain with the -C≡N as a substituent.
- Chain is numbered so as to give the -C≡N group the lowest possible locant number
- E.g.
1-cyanopropane
Nitrile Style
• The nitrile suffix is used in a very similar manner to carboxylic acids
• Faced with same compound, CH3CH2CH2C≡N• Functional group is a -C≡N, therefore suffix = -
nitrile• Hydrocarbon structure is an alkane therefore –
Longest chain is C4• Butanenitrile
Naming Nitriles (nitrile style)
• Benzonitrile
• Cyclopentanecarbonnitrile
Naming Nitriles
• Butanedinitrile
• 2-methyl-1-propanenitrile• Bonus! How do you name this?
Nitro Functional Group
RNO2
Nitro Functional Group• O-N=O• central nitrogen atom is involved in both a
double bond and a single bond• Highly explosive, various impurities or
improper handling can easily trigger a violent exothermic decomposition (aka an explosion)
• An example is nitroglycerin
Nitro R-NO2
• Aromatic nitro compounds.• Trinitrotoluene (TNT)- A pale yellow, solid organic nitrogen
compound used chiefly as an explosive, prepared by stepwise nitration of toluene
Reactions: Reduction
• Nitro compounds are reduced to amines• RNO2 + 3 H2 → RNH2 + 2 H2O
Naming Nitro Compounds
• Simply name the -NO2 as a nitro substituent
Naming Nitro Compounds
• Nitromethane• Guess how Nitrobenzene looks like?
Thiol Functional Group
Thiols
• Organosulfur compound that contains a carbon-bonded sulfhydryl (-C-SH or R-SH) group
• Have a foul smell• Structurally similar to an alcohol but contains
a sulfur atom in place of the oxygen atom normally found in an alcohol.
• Among the odorous principles in the scent of skunks and of freshly chopped onions
Synthesis
• Reaction of related alcohol with hydrogen sulphide
• CH3OH + H2S → CH3SH + H2O
Naming Thiols
• Sulfur analogues of alcohols• Named the same way too• The root name is based on the longest chain
with the -SH attached.• The chain is numbered so as to give the thiol
unit the lowest possible number. • The thiol suffix is added after the hydrocarbon
suffix : e.g. -ane + -thiol = -anethiol or -ene + thiol = -enethio
Naming Thiols• CH3CH(SH)CH3
• Propan-2-thiol or 2-propanethiol
• 1-Butanethiol
• Cyclopentanethiol
Naming Thiols
• 4-methylpentan-2-thiol
Sulphide Functional Group
Also known as Thioether
Sulphides
• S atom bonded to two C atoms via s bonds• R-S-R• Named the same way as oxygen cousins,
ethers• Like many other sulfur-containing compounds,
volatile thioethers characteristically have foul odors
Naming Sulphides: "Simple" thioethers
• "Simple" thioethers• If both groups are simple alkyl groups, then
the thioether is usually named as alkyl alkyl thioether
• Alkyl groups are listed in alphabetical order• If the two alkyl groups are the same, then it's
a dialkyl thioether• CH3-S-CH3 Dimethylsulphide
• CH3CH2SCH3
Ethyl Methyl Sulphide
Intermediate Thioethers
• If one of the groups is more complex then the thioether group is usually treated as an alkylthio- (i.e. R-S-) substituent.
• The more complex group (i.e. longer chain, more branched, other substituents) defines the root
• CH3CH2CH2SCH3
1-methylthiopropane
Complex Thioethers• If both groups are complex then the ether can
be named using –thio• E.g. CH3SCH2CH2CH3
• Hydrocarbon structure is an alkane Functional group is an thioether, therefore prefix = -thio-
• The longest continuous chain (including the S) is 5 therefore root = pent
• Numbering from the left as drawn to make the thio group locant 2-
• 2-thiopentane
Examples (Simple)
• Butyl ethyl sulphide
Disulphides
Disulphide bond
• Covalent bond, usually derived by the coupling of two thiol groups
• Also known as sulphide bridge
Disulphide Bond
• Play an important role in the folding and stability of proteins
• E.g. two-amino-acid peptide cystine• Composed of two cysteine amino acids joined
by a disulfide bond
Ever wondered why hair doesn’t seem to decompose along with dead bodies?
• Over 90% of the dry weight of hair comprises proteins called keratins from the amino acid cysteine
• Hair has a high disulfide content• The robustness conferred in part by disulfide
linkages• Recovery of virtually intact hair from ancient
Egyptian tombs