Chapter 5: Reactivity Centers: Functional Groups

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.

• 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

• 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).

  

• 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.
• \

@@How ethereal@@

==Carbonyl Compounds==

@@Living on the edge: Aldehydes@@

@@Stuck in the middle: Ketones@@

@@Carboxylic acids@@

@@Sweet-smelling compounds: Esters@@

@@Nitrogen-containing functional groups@@

@@I am what I amide@@

@@Be nice, don’t be amine person@@

==Test Your Knowledge==