Lecture 2 - Hydrocarbon nomenclature

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Functional groups
1. Method of grouping organic compounds by similar groupings of atoms called functional groups.
2. These groupings of atoms have similar structure and chemical reactivity.
3. Groupings
  1. Hydrocarbons - contain only hydrogen and carbon. Alkanes, Alkenes, Alkynes, and aromatic
  2. Carbon single bonded to an electronegitive atom. alkyl halides, alcohols, ethers, amines
  3. Carbon-oxygen double bonds. aldehydes, ketones, carboxylic acids, anhydrides, esters, & amides.
4. Functional groups will have specific suffix and prefix designations.
Introduction to nomenclature
1. Early in the history of organic chemistry there were not many compounds
2. Applying trivial names was not that much of a concern. Not that many combinations
3. Today with so many compounds, a method was needed to uniquely name a structure and have the name describe the structure
4. Current system was developed by IUPAC (International Union of Pure and Applied Chemistry)
5. Form of naming is Prefix–Parent–Suffix
  1. Parent is the longest continous carbon chain
  2. Suffix is the family of the compound
  3. Prefix is location of functional groups.
Naming Alkanes
1. Main chain
  1. Alkanes are saturated hydrocarbons. Just single bonds between carbons.
  2. Straight chain alkanes are named for their number of carbons
  3. First three are of historical origin, the rest follow Greek numbers.
  4. These compound act was the based for the Parent part of IUPAC nomenclature.
  5. The suffix for alkanes is -ane
2. Substituents
  1. As alkanes become more complicated the chain can have many branches. The groups that lay off of the longest chain are named substituents.
  2. These substituents are names alkyl groups.
  3. Name formed by the chain length name -yl. Ex methyl ethyl
  4. For larger numbers of carbons there are more possibilities.
  5. General patterns
    1. Primary - a carbon has one other carbon attached
    2. Secondary - carbon has two other carbons attached
    3. Tertiary - 3 carbons attached
    4. Quarternary - 4 carbons attached
  6. Isomeric substituents
    1. Just like with isomers, with more carbons many patterns with the same number of carbons are possible.
    2. Have both "common names" and systematic names.
    3. n-
      1. No branching
      2. Ex. n-propyl, n-butyl
    4. sec-
      1. Stands for "secondary"
      2. Point of attachment to a main chain is secondary within the substitutent
      3. Ex. sec-butyl,
    5. tert -
      1. Point of attachment is tertiary
      2. Ex. tert-butyl
    6. iso-
      1. Names for substituents with less than 7 carbons with a single branch at one end and point of attachment at the other
      2. Ex. isopropyl, isobutyl
3. Steps to naming
  1. Find the longest continuous chain.
    1. Does not have to be straight
    2. Parent is the number of carbons
    3. Since is an alkane, suffix is -ane
  2. Number carbons on the main chain
    1. Select numbering that gives the lowest values for subsitiuents
    2. Ex. 2-methylpentane is not 4-methylpentane
  3. Identify substituents
    1. Crosses with step 2
    2. substituents are numbered by the carbon that they are attached to.
    3. If a carbon has many substituents all of the attachments have that carbons number.
    4. Substituents become the prefix
  4. Name is written as a single word
    1. Use hyphens to separate numbers from different prefixes
    2. Commas separate the numbers of the same substituents
    3. Identical substituents use prefixes di-, tri-, tetra
    4. substituents are listed alphabetically, excluding numeric prefixes (di, tri- etc)
Naming Alkenes and Alkynes
1. Steps
  1. Just as with alkanes find the longest chain containing the multiple bond
    1. Alkene are double bonds. Suffix -ene
    2. Alkyne are tripple bonds. Suffix -yne
  2. Number chain
    1. Number so that unsaturated carbons have the smallest number
    2. When apparent, such as with cycloalkenes, the substituents are the lowest possible number combination.
  3. Write full name
    1. Same prefix rules apply as with alkanes.
    2. Give multiple bond position by using the number of the first carbon the bond.
    3. Multiple double bonds named as -diene, triene etc.
  4. Old names
    1. For older compounds can use older names.
    2. Ex. ethene -> ethylene. propene -> propylene
    3. ethyne -> acetylene
2. Geometric isomers
  1. Mentioned last week that alkenes can have isomeric forms
  2. Isomers are named for the position of groups on either side of the double bond
  3. cis- same side, trans opposite sides.
Cyclic alkanes
1. Structure
  1. Carbons form a ring
  2. Since form a ring are more constricted than straight chain alkanes
  3. Most stable are where the bond angle is closets to a straight chain.
  4. 5 and 6 member rings are some of the most stable and most common
  5. 3 and 4 member rings exist, but are less stable and less common.
2. Nomenclature
  1. Parent name derived from number of carbons on the ring and placing cyclo before it. Ex. Cyclehexane
  2. With just one substituent don't need to number. Ex. methylcyclohexane.
  3. With more than one substituent, give group with the highest priority the lowest number. Ex 1-ethyl-3-methyl cyclohexane.
Aromatic compounds
1. Structure of Aromatic compounds
  1. Aromatic usually refers to compounds containing benzene
  2. Has a different behavior than alkenes.
  3. Not complete same reactions, hydrogenation, bromination etc.
  4. Non-reactive nature is linked to its structure. Resonance and ring of electrons.
  5. Drawn with lines or also with circle
  6. Compounds what show more stability than there alkane counter parts are termed aromatic
2. Naming Aromatic compounds
  1. Substituted benzene rings use -benzene as the parent root. Ex. Bromobenzene, nitrobenzene
  2. Number not used for mono substituted bezenes
  3. Two substituents ortho 1,2 ; meta 1,3; para 1,4. Ex. ortho-dibromobenzene, meta-chloronitrobenzene, para-dimethylbenzene
  4. Some common substituents have special names. Toluene, phenol, aniline, xylene, benzoic acid, beznaldehyde.
  5. Benzene ring can be a substituent. phenyl