Chapter 5: Reactivity Centers: Functional Groups

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Organic Chemistry for Dummies 2nd Edition by Arthur Winter, PhD

Chapter 5: Reactivity Centers: Functional Groups

Functional groups: carbons forming stable bonds to other non-carbon atoms, forming reactive centers.

==Hydrocarbons==

  • Hydrocarbons: molecules that contain just hydrogen and carbon.

    • Includes:

    • Alkanes: contain only single bonds and are generally not considered a functional group.

      • Inert under most conditions
    • Alkenes: molecules containing carbon-carbon double bonds)

    • Alkynes: molecules containing carbon-carbon triple bonds

    • Aromatics: double-bond-containing ring systems.

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  • Simple hydrocarbons: usually cheap and commercially availble because they’re found as components in crude oil.

@@Double the fun: The alkenes@@

General form of an alkenes:

  • The R is an abbreviation for the rest of the molecule.

    • Most often implies a hydrogen atom or a hydrocarbon group

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  • Alkenes: found in natural products (compounds isolated from living organisms).

  • Alkenes are also used commercially.

    • Ethylene polymerizes to make polyetylene (type of plastic used in grocery bags, milk bottles, etc.)
    • Polymerize: combines many small units to make large molecules.
  • Alkenes can also be arrnaged into rings like in cyclopropene (but this is generally not a favorable shape for them to stay in).

  • They are important to organic chemistry because they are the “go-betweens” in the synthesis of complex molecules.

  • The names of alkenes generally end with the suffix –ene.

@@Alkynes of fun@@

General form of alkynes:

  • The simplest alkyne is, acetylene, which has the 2 R groups substituted with hydrogen.
    • It is a gas that is used as a welding fuel.
  • Alkynes are less common than alkenes in nature, but there are some out there.
  • Alkynes prefer to have bond angles of 180 degrees, where the triple bond and the two R groups on either side lie in a straight line.
    • Triple bonds do not stretch much, so molecules with triple bonds are generally unstable in rings of fewer than eight carbons.
  • Alkyne names end with the suffix –yne.

@@Smelly compounds: The aromatics@@

  • They are also called ‘arenes’.
  • Aromatics: consist of rings containing alternating double bonds.
    • Example: Benzene (a six-carbon ring with three alternating double bonds).

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  • Aromatics have a special property that makes them significantly more stable and less reactive than alkenes.
  • They are called aromatics because the first of these compounds to be discovered (before their structures were determined) had funky smells.
  • Many compounds made by living organisms contain aromatic rings.

==Singly Bonded Heteroatoms==

  • Heteroatoms: atoms other than carbon or hydrogen.
    • Include such important atoms as the halogens, oxygen, and sulfur.
    • These are the components of the halide, alcohol, ether, and thiol functional groups.

@@Happy halides@@

  • Halides are organic compounds that contain one or more halogens.

    • 4 halogens that you frequently see in organic compounds: fluorine, chlorine, bromine, and iodine.

    • General form of halides:

  • Halides are not common in the natural world., and when they are found, they’re often in compounds that are toxins.

    • Commercially, halides are used as propellants in aerosol cans such as hairspray and spray paint, solvents such as chloroform, and as refrigerants.
    • Also as insecticides such as DDT. This is banned in the United States because it has caused unwanted harmful side effects in wildlife and in humans.

@@For rubbing and drinking: Alcohols@@

  • Alcohols consist of the general formula R-OH.

  • The names end with the suffix -ol.

  • Some examples include: ethanol (alcohol found in beer, wine, and liquor), isopropanol (rubbing alcohol), and ethlene glycol (used in antifreeze).

  • Alcohols are also found in natural products.

    • Like, sugar contains many -OH groups.

@@What stinks? Thiols@@

  • They are foul-smelling compounds and contain the formula R-SH.
  • Thiols: sulfur analog of alcohols/in other hideously unpleasant compounds.
    • Like: flatulence, garlic, sewage, skunk spray, etc.
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@@How ethereal@@

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==Carbonyl Compounds==

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@@Living on the edge: Aldehydes@@

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@@Stuck in the middle: Ketones@@

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@@Carboxylic acids@@

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@@Sweet-smelling compounds: Esters@@

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@@Nitrogen-containing functional groups@@

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@@I am what I amide@@

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@@Be nice, don’t be amine person@@

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==Test Your Knowledge==

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