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Organic Chemistry 1


 
 

Types of Organic Molecules and Functional Groups

Hydrocarbons: molecules that contain only carbon and hydrogen

  1. Aliphatic hydrocarbons: Do not contain a benzene ring or any other aromatic system.

    1. Alkanes: Aliphatic hydrocarbons that contain only single bonds and do not contain rings of bonded atoms; also called saturated hydrocarbons.

      • General formula CnH2n + 2, where n is an integer.

    2. Alkenes: Unsaturated hydrocarbons containing one or more carbon-carbon double bonds.

      • General formula CnH2n + 2 - 2d, where d = # of double bonds in the molecule and n is an integer.

    3. Alkynes: Unsaturated hydrocarbons containing one or more carbon-carbon triple bonds.

      • General formula CnH2n + 2 - 4t, where t = # of triple bonds in the molecule and n is an integer.

    4. Cycloalkanes: Unsaturated hydrocarbons containing one or more rings of bonded carbon atoms.

      • General formula CnH2n + 2 - 2r, where r = # of rings in the molecule and n is an integer.

      • Tend not to be flat because of the tetrahedral bond angle requirements of carbon.

      • Cyclopentane (C5H10) and cyclohexane (C6H12) are the most stable cycloalkanes; other cycloalkanes have more ring strain (i.e., destabilization of a ring due to the bond angles of atoms in a ring deviating from the 109.5 preferred by sp3-hybridized carbons).

  2. Conjugated hydrocarbons: Hydrocarbons containing a series of three or more overlapping p orbitals (e.g., a series of alternating double and single bonds); conjugation contributes to the stability of a molecule, due to the delocalization of π electrons over the length of the conjugated system.

  3. Aromatic hydrocarbons: Special type of conjugated molecule containing a benzene ring or some other aromatic system; unusually stable because of their unique electronic configuration and delocalization of π electrons.

    1. Benzene: C6H6; the parent compound of the aromatic hydrocarbon family.

    2. Arenes: Benzene derivatives in which one or more hydrogen atoms from benzene are replaced by other functional groups.

    3. Huckel’s Rule: A molecule is aromatic if it contains a planar, cyclic, conjugated system possessing 4n + 2 (where n is an integer) π electrons.

Functional groups:

Atoms or groups of bonded atoms that bond to carbon atoms to give rise to other families of organic compounds. A given functional group will generally undergo the same type of reactions regardless of the molecule in which it appears. When a functional group is bonded to an atom, it is called a substituent of that atom.

Degree of alkyl substitution:

Number of alkyl group substituents on a given atom (usually carbon). An atom that has alkyl substituents can be primary(one alkyl substituent), secondary (two alkyl substituents), tertiary (three alkyl substituents), or quaternary (four alkyl substituents).

Common organic functional groups

Classes of molecules:

  1. Alcohols: Molecules containing one or more hydroxyl groups bonded to alkyl groups.

  2. Alkyl halides: Molecules containing one or more halogen atoms bonded to alkyl groups.

  3. Amines: Molecules containing one or more amino groups bonded to alkyl groups.

  4. Ethers: Molecules containing two alkyl groups bonded to the same oxygen atom.

    • Epoxides: Ethers containing an oxygen atom bonded to two other carbon atoms in a three-membered ring.

  5. Carbonyls: Molecules containing one or more carbonyl groups.

    1. Aldehydes: Molecules containing a carbonyl group bonded to a hydrogen atom and an alkyl group.

    2. Ketones: Molecules containing a carbonyl group bonded to two alkyl groups.

    3. Carboxylic acids: Molecules containing a carbonyl group bonded to a hydroxyl group and an alkyl group.

    4. Esters: Molecules containing a carbonyl group bonded to an alkoxy group and an alkyl group.

    5. Acid chlorides: Molecules containing a carbonyl group bonded to a chloride group and an alkyl group.

    6. Amides: Molecules containing a carbonyl group bonded to an amino group and an alkyl group.

  6. Common classes of organic molecules

IUPAC rules: A system set forth by the International Union of Pure and Applied Chemistry (IUPAC) for naming organic molecules.

  1. IUPAC rules for alkane molecules

    1. Count the number of carbon atoms in the longest continuous carbon chain in the molecule. Based on the number of carbon atoms in the chain, write its name as if it were a simple straight-chain alkane. This name is the base of the name of the whole molecule.

      • If the molecule contains multiple chains of equal length, the parent chain is the one that has the most branch off points.

       
      Carbons   Alkane name
       
      1   Methane
       
      2   Ethane
       
      3   Propane
       
      4   Butane
       
      5   Pentane
       
      6   Hexane
       
      7   Heptane
       
      8   Octane
       
      9   Nonane
       
      10   Decane
       
      11   Undecane
       
      12   Dodecane


    2. Number each carbon atom in the parent chain, starting from the end of the chain closer to its nearest branch off point. If both ends of the chain are the same distance from their nearest branch-off points, start from the end closer to its second-nearest branch-off point.

    3. Consider every branch-off of the parent chain to be a separate hydrocarbon. Name each branch based on its length, but replace the ending “-ane” with “-yl.” For each branch, note the number (from Step 2) of the carbon atom on the parent chain to which it is attached and precede the branch name with this number. If there are two or more identical branches off of the main chain, separate the numbers of the carbons to which the identical substituents are attached with commas, and precede the name of the branch with the appropriate numerical prefix (di-, tri-, etc.).

    4. Write out the name of the molecule by adding the branch names from Step 3 (in alphabetical order, ignoring the branch numbers and numerical prefixes) to the name of the parent chain from Step 1.

  2. Naming an alkane molecule

  3. IUPAC rules for molecules containing other functional groups:

    1. Alkenes: Follow the rules for naming alkanes, but choose the longest carbon chain containing the double bond as the parent chain in Step 1, and begin numbering the parent chain with the carbon closest to the double bond in Step 2. Change the ending of the parent chain name from“-ane” to “-ene,” and indicate the position of the double bond by preceding the name of the parent chain with the number of the first carbon involved in the double bond.

    2. Alkynes: Follow the rules for naming alkenes, changing the ending of the parent chain name from “-ene” to “-yne.”

    3. Alkyl halides: Follow the rules for naming alkanes, and name halogen substituents as if they were branches off of the main carbon chain; when naming halogen substituents, change the ending “-ine” to “-o.”

    4. Alcohols: Follow the rules for naming alkenes, changing the ending of the parent chain name from “-ene”to “-anol.”

    5. Amines: For primary amines (RNH2), name the alkyl substituent as if it were a branch on an alkane parent chain, and attach the suffix “-amine.” For secondary and tertiary amines, choose the largest alkyl substituent on the nitrogen atom as the parent chain and change its ending from“-ane” to “-ylamine,” and then name the other alkyl groups as substituents on the main chain at the “N” position.

    6. Ethers: Name each substituent attached to oxygen separately. Attach them in alphabetical order to the word “ether.”

    7. Aldehydes: Follow the rules for naming alkanes, but in Step 1 choose the longest carbon chain containing the aldehyde group as the parent chain, and change the ending of the parent chain name from “-ane” to “-anal.”

    8. Ketones: Follow the rules for naming alkanes, but choose the longest carbon chain containing the carbonyl carbon as the parent chain in Step 1, and begin numbering the parent chain with the carbon closest to the carbonyl carbon. Change the ending of the parent chain name from “-ane” to“X-one,” where “X” is the number of the carbonyl carbon.

    9. Carboxylic acids: Follow the rules for naming alkanes, but choose the longest carbon chain containing the carboxylic acid group as the parent chain in Step 1, begin numbering from the carbonyl carbon in Step 2, and change the ending of the parent chain name from “-ane” to “-anoic acid.”

    10. Acid chlorides, amides, and esters: Follow the rules for naming carboxylic acids, but change the ending“-ic acid” to “-yl chloride” (acid chlorides), “-amide”(amides), or “-ate” (esters).