functional group
DESCRIPTION
Functional Group. Atom or group of atoms that replaces a hydrogen atom in a hydrocarbon. Functional groups give the molecule personality. Functional Group. Each functional group gives the molecule distinctive chemical & physical properties. - PowerPoint PPT PresentationTRANSCRIPT
Functional Group
•Atom or group of atoms that replaces a hydrogen atom in a hydrocarbon.•Functional groups give the molecule personality.
Functional Group
•Each functional group gives the molecule distinctive chemical & physical properties.•Molecules with functional groups contain at least one atom that is not C or H. Not hydrocarbons!
Names of molecules with functional group
•Derived from the name of the hydrocarbon with the same number of carbon atoms.
Halides or halocarbons or alkyl halides
•One or more H in an alkane is replaced with a halogen (F, Cl, Br, or I).•General formula = R-X.
–X is the halogen.–R is the alkyl branch.
Properties of Halides
•Likely to be polar molecules, unless very symmetric.
•Dipole-dipole interactions.
Polar Molecules
•Have POLES.
•The electron cloud is lop-sided. One end of molecule is electron-rich & the other electron-poor.
•Dipole-dipole interactions.
Polar Molecules
•Atoms in molecule have very different electronegativities.
•Molecule is not symmetrically shaped.
Properties of Halides
•HigherHigher mp, bp, Hf, Hv than the corresponding alkanes.•LowerLower rate of evaporation & vapor pressure than the corresponding alkanes.
Alcohols
•One or more hydrogens in a hydrocarbon replaced with an OH group.
•General formula = R-OH.
•The OH or hydroxyl group does NOT ionize in water.
Properties of Alcohols
•NONelectrolytes. No H+ or OH- ions in solution. •Do NOT turn litmus red, etc.
Properties of Alcohols
•Contain O-H bond. Molecules tend to be polar. Dissolve in water. •Hydrogen bonding takes place between alcohol molecules. Higher mp, bp than corresponding alkanes.
Classification of alcohols by number of -OH groups.
•Monohydroxy:Monohydroxy: 1 -OH group.•Dihydroxy:Dihydroxy: 2 –OH groups.•Trihydroxy:Trihydroxy: 3 -OH groups.
Further classification of monohydroxy alcohols by carbon to
which OH group attached.
•Primary:Primary: OH group at end carbon.•Secondary:Secondary: OH group on middle carbon.•Tertiary:Tertiary: OH group at branch-point carbon.
Ethers
•Contain an O atom bridge connecting 2 alkyl branches.
•General Formula: ROR‘
•R & R‘ are alkyl groups (the 2 branches).
•R & R‘ can be same or different.
Properties of ketones
Carbonyl group is quite polar. Tend to be soluble in
both polar & nonpolar solvents.
Naming Esters
1. Name alkyl branch next to bridge O.
2. Name branch with carbonyl group.
3. Replace –e of corresponding alkane name with -oate.
Amines
1. Replace H in an alkane with –NH2 group.
2. Replace final –e in alkane name with amine.
3. # gives location of NH2 group.
4. Analogous to alcohols
Properties of Amines
1. Tend to smell really bad.
2. Contain N-H bond. Exhibit H-bonding between molecules.
Naming Amides
1. Find name of corresponding alkane.
2. Drop final -e & add –amide. 3. Never need a # - Always at
the end.