orgo quiz 3

Question 1

properties of alkanes

Answer 1

• saturated hydrocarbons
• hydrophobic
• strong, nonpolar bonds (not very reactive)
• only LDFs so longer molecules have the greatest IMFs and boiling points

Question 2

reactions with alkanes

Answer 2

*can be oxidized with very high heat!
- halogenation
- “cracking”: longer alkanes broken into smaller ones
- combustion: releases energy in the presence of oxygen

Question 3

analyzing stability from alkane combustion reactions

Answer 3

• combustion from oxidation of alkanes releases energy by formation of new bonds in CO2
• smaller energy release = more stable alkane reactants
• straight-chain alkanes are the least stable, as well as cycloalkanes with small bond angles
• branched alkanes are the most stable bc of delocalization

Question 4

names for alkanes with 1-10 carbons

Answer 4

methane
ethane
propane
butane
pentane
hexane
heptane
octane
nonane
decane

Question 5

naming propanes when added to other functional groups

Answer 5

• normally “propyl”
• “isopropyl” = 3 isometric carbons

Question 6

naming butanes when added to other functional groups

Answer 6

• “n-butyl” = chain
• “sec-butyl” = func. group on second carbon
• “tert-butyl” = func. group stems from central C that other 3 C branch from
• “isobutyl” = 3 isometric carbons with func. group branching off one end

Question 7

rules for IUPAC nomenclature

Answer 7

1. identify longest continuous C chain (or ring)
2. number chain from end near first substituent (or if even whatever end gives lowest overall substituent numbers)
3. identify and number substituents
4. combine and alphabetize (substituents first disregarding prefixes)

Question 8

prefixes when there’s multiple of the same substituent group

Answer 8

di = 2
tri = 3
quad = 4

Question 9

cycloaklanes

Answer 9

• unsaturated (extra C bond)
• bond angles restricted based on ring size, so slightly more reactive than alkanes!
• when combined with alkanes, name based on whatever is longer (ring or chain) and other group becomes a substituent

Question 10

parts of molecular structure

Answer 10

1. composition
2. connectivity
3. conformation
4. stereochemistry

Question 11

conformational isomers

Answer 11

• same structural isomer
• rapidly interconverting structures in equilibrium

Question 12

torsional strain

Answer 12

• e- repulsions during eclipsing
• even staggered conformation has some, but we consider it to be 0

Question 13

steric strain

Answer 13

2 groups trying to occupy the same space and colliding
- bigger group = more strain