Quiz 2 Flashcards
Alkanes
- Flammable! Undergoes combustion reactions
- Nonpolar
- Melting and boiling points are directly proportional to the strength of intermolecular forces
- Strength of London dispersion forces between molecules are directly proportional to the surface area of the molecules
Flammable! Undergoes combustion reactions
alkane + O2 (excess) = CO2 (g) + H2O (g) + energy
alkane + O2 (difficient) = C (s) + 2 H2O (g)
CO (g) + 2 H2O (g)
Nonpolar
- Immiscible (i.e. do mix) with water or other polar molecules
- Very weak London dispersioin forces keep molecules attracted to one another
Strength of London dispersion forces between molecules are directly proportional to the surface area of the molecules
- Boiling points increase substantially with molecular weight
- Boiling points decrease somewhat with braching; i
propane
C3H8, -42 C
butane
C4H10, 0 C
2,2-dimethylpropane
C5H12, 10 C
2-methylbutane
C5H12, 28 C
pentane
C5H12, 36 C
hexane
C6H14, 68 C
1 – 4
gas, heating fuels (natural gas)
5 – 8
volatile, gasoline, non-polar solvents
-liquid evaporates quickly at high vapor pressure
9 – 17
“stable”, kerosene, diesel, jet fuel
18+
“stable”, lubricating oil, asphalt
ALKENES
contains a C = C (unsaturated)
vs. alkanes: more reactive, slightly lower BP/MP
ethane
30 g/mol
BP = 185 K (-89˚C)
ethene (ethylene),
28 g/mol
BP = 170 K
propane
44 g/mol
BP = 231 K
propene (propylene),
42 g/mol
BP = 226 K
butane
58 g/mol
BP = 274 K
1-butene
56 g/mol
BP = 267 K
trans-2-butene
BP = 274 K
cis-2-butene
BP = 277 K
CIS-TRANS ISOMERS
C – C bonds rotate freely
C = C bonds locked into place
Cis
non-H substituents on the same side
trans
non-H substituents non-H substituents
HYDROGENATION
H2 w/ Pt/Pd/Ni catalyst
BROMINATION
Br2 w/ light catalyst
HYDRATION
H2O w/ H2SO4 catalyst
ADDITION REACTIONS
OH attaches to C with most number of substituents
If same on both ends of C = C: two products are formed
Aromatic ring
: 6-membered ring with alternating C=C & C – C bonds
3 double bonds: actually spread out
delocalized electrons
mostly unreactive C = C
Aromatic ring ex
benzene
C6H6 (major carcinogen!)
ALTERNATIVE SUBSTITUENT LOCATION NOMENCLATURE: for two substituents
1,2 = “ortho” (adjacent) 1,3 = “meta” 1,4 = “para” (opposite
benzoic acid
food preservative
benzaldehyde
almond smell
phenol
old disinfectant (Joe Lister)
aniline
precursor to polyurethane
rotten fish smell
toluene
indust. Solv.
rec. inhalant
substituents:
Different functional groups attached to benzene