An Introduction to Organic Compounds

1
An Introduction to Organic Compounds

• Nomenclature, Physical Properties, and
  Representation of Structure

2
Note from Dr. Maynes

• I found this PowerPoint on the web. It is very
  comprehensive, and as far as I can see, correct.
• However, it includes a lot of common names,
  which I am NOT recommending you learn at this
  point
• Feel free to use this to enrich your study of
  Organic Nomenclature

3
Contents of Chapter 2

• Nomenclature
• Structures of Alkyl Halides, Alcohols, Ethers,
  and Amines
• Physical Properties
• Conformations of Alkanes
• Cycloalkanes

4
Counting to Ten in Organic

• 01 meth Mother
• 02 eth Enjoys
• 03 prop Peanut
• 04 but BUTter
• 05 pent PENTagon
• 06 hex HEXagon or HEX nut
• 07 hept HEPTember (Roman sept is Greek hept)
• 08 oct OCTober
• 09 non NONember (Roman nov is Greek non)
• 10 dec DECember

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Alkanes
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Primary, Secondary, Tertiary

• A primary carbon has one other C directly bonded
  to it.
• A secondary carbon is directly bonded to two
  other Cs.
• A tertiary carbon is directly bonded to three
  other Cs.
• Multivalent atoms are 1º, 2º, or 3º by bonding to
  Cs.
• Univalent atom or group not really 1º, 2º, or 3º
  on its own - ID depends on type of carbon it is
  bonded to.

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Nomenclature of Alkyl Substituents

• There are four alkyl groups that contain four
  carbons

8
Nomenclature of Alkyl Substituents

• The prefix sec- occurs only in sec-butyl

9
Nomenclature of Alkyl Substituents

• The prefix tert- can be used with butyl or pentyl
  (also known as amyl) but not with hexyl

10
IUPAC Systematic Nomenclature - Alkanes

1. Determine longest continuous chain (i.e. parent
   hydrocarbon)
2. Cite the name of substituent before the name of
   the parent hydrocarbon along with the number of
   the carbon to which it is attached

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IUPAC Systematic Nomenclature - Alkanes

1. Number in the direction that gives the lower
   number for the lowest-numbered substituent.
   Substituents are listed in alphabetical order
   neglecting prefixes such as di- tri- tert- etc.

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IUPAC Systematic Nomenclature - Alkanes

1. When both directions yield the same lower number
   for the lowest numbered substituent, select the
   direction that yields the lower number for the
   next lowest numbered substituent

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IUPAC Systematic Nomenclature - Alkanes

1. If same substituent numbers are obtained in
   either direction, number in direction giving
   lowest number to the first named substituent

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IUPAC Systematic Nomenclature - Alkanes

1. If compound has two or more chains of the same
   length, parent hydrocarbon is chain with greatest
   number of substituents

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IUPAC Systematic Nomenclature - Alkanes

• Names such as sec-butyl and tert-butyl are
  acceptable, but systematic substituent names are
  preferable
• Numbering of the substituent begins with the
  carbon attached to the parent hydrocarbon
• This number together with the substituent name
  is placed inside parentheses

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Nomenclature of Cycloalkanes

• Cycloalkanes generally are shown as skeletal
  structures

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Nomenclature of Cycloalkanes

• Ring is the parent hydrocarbon unless the alkyl
  substituent has more carbons in that case the
  substituent becomes the parent hydrocarbon
• If only one substituent, no need to give it a
  number

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Nomenclature of Cycloalkanes

1. If the ring has 2 substituents, list in
   alphabetical order and give number 1 to first
   named group

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Nomenclature of Cycloalkanes

1. If there is more than one substituent, list in
   alphabetical order one substituent is given the
   position number 1 number either clockwise or
   counterclockwise - lowest numbers

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Nomenclature of Alkyl Halides

• Common name - Name the alkyl group first,
  followed by the name of the halogen expressed as
  an -ide name

21
Nomenclature of Alkyl Halides

• IUPAC name - The halogen is treated as a
  substituent

22
Nomenclature of Ethers

• Common name - Name(s) of alkyl group(s) listed
  first followed by the word ether

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Nomenclature of Ethers

• IUPAC name - The smaller alkyl group is converted
  to an alkoxy name and used as a substituent

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Nomenclature of Alcohols

• Common name - Name of the Alkyl group followed by
  the word alcohol

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Nomenclature of Alcohols

• IUPAC name - The OH group is a site of reactivity
  (a functional group)
• Functional group is denoted by the suffix, ol

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IUPAC Nomenclature of Alcohols

1. Parent Hydrocarbon is the longest continuous
   chain that contains the OH
2. Number the chain in direction that gives
   functional group the lowest number
3. If both a substituent and a functional group are
   present, the functional group gets the lower
   number

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IUPAC Nomenclature of Alcohols

1. If the functional group gets the same number when
   counted from both directions, use direction which
   gives the substituent the lower number
2. If there is more than one substituent, cite
   substituents in alphabetical order

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IUPAC Nomenclature of Alcohols

• System is summarized as Substituent Parent
  Hydrocarbon Functional Group

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Nomenclature of Amines

• Common name - Name of the Alkyl group(s) (in
  alphabetical order) followed by the syllable
  amine
• The whole name is a single word

methylamine methylpropylamine
30
Nomenclature of Amines

• IUPAC name - The NH2 group is a site of
  reactivity (a functional group)
• Functional group is denoted by the suffix,
  amine
• Final e of longest alkane group replaced by
  suffix amine

1-butanamine butan-1-amine
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IUPAC Nomenclature of Amines

• Find the longest chain bonded to the nitrogen
• Final e is replaced with amine
• Number the carbon to which nitrogen is bonded
• Number any substituents on the alkyl chain
• Use italicized N- for each additional
  substituent(s) on the nitrogen

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Properties of Alkyl Halides, Alcohols, Ethers,
Amines

• For alkanes, there are only induced
  dipole-induced dipole interactions (also known as
  van der Waals forces or London forces)
• van der Waals forces are a function of surface
  area

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Induced Dipole-Induced Dipole Interactions
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Hydrogen Bonding Strong Dipole-Dipole
Interactions
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Dipole-dipole Interactions

• Particularly important for ethers vs. alkanes
• Ethers and alkyl halides have dipole moments, but
  their intermolecular attractions are not as
  strong as hydrogen bonds

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Comparative Boiling Points
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Solubility

• The more carbons that are present, the less
  soluble an organic compound is in water

38
Newman Projections

• A convenient way to describe conformation isomers
  is to look at the molecule along the axis of the
  bond of interest
• A Newman projection is a graphical representation
  of such a view

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Conformations of Alkanes Rotation About C-C
Single Bonds
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Chair Conformation of Cyclohexane
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Drawing Cyclohexane in the Chair Conformation
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Interconversion of Cyclohexane Conformations

• As a result of simultaneous rotation about all
  C-C bonds, a chair conformation of cyclohexane
  can interconvert to another chair conformation by
  a ring-flip
• In the process, equatorial bonds become axial and
  vice versa

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Monosubstituted Cyclohexanes

• When there is one substituent on the cyclohexane
  ring, the two chair conformations are no longer
  equivalent

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Conformations of 1,4-Disubstituted Cyclohexanes
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Conformations of 1,4-Disubstituted Cyclohexanes

• The cis isomer must have one substituent in an
  axial position and one in an equatorial position

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Conformations of 1,4-Disubstituted Cyclohexanes

• The trans isomer has both substituents in either
  the equatorial or in the axial positions

47
Conformations of cis-1,3-Disubstituted
Cyclohexanes

• A cis-1,3-disubstituted cyclohexane can exist in
  one of two conformations

48
Conformations of trans-1,3-Disubstituted
Cyclohexanes

• Both conformers of trans-1-tert-butyl-3-methylcycl
  ohexane have one substituent in an axial position
  and one in an equatorial position