Alkanes, Alkenes, Alkynes Flashcards
Why do hydrocarbons tend to have low boiling points?
Hydrocarbons dont have strong intermolecular interactions. Think about water. Water has hydrogen bonds that need to break in order for water to boil. No such bonds are present in hydrocarbons. The main interaction these compounds have are weak hydrophobic interactions.
Identify the arrangement
Sec-butyl
How do the presence of double and triple bonds impact reactivity of hydrocarbons?
Hydrocarbon reactivity increases as electron density is increased. Double bonds increase electron density and triple bonds increase it even more. So molecules with triple bonds will be more reactive than those with double bonds and those with only single bonds will be the least reactive.
How do you identify a conjugated system?
Alkenes with alternating carbon-carbon double bonds form conjugated systems. 1,3,5-hexatriene has alternating double bonds, making it a conjugated system also 2,4,6-heptatriene has alternating double bonds, making it a conjugated system.
Ethene is exposed to H2 in a solution containing a chunk of solid palladium. If it reacts successfully, the original alkene will…
Be reduced to ethane
A 5 carbon alkane would have what prefix?
Penta
A 7 carbon alkane would have what prefex?
Hepta
A 9 carbon alkane would have what prefex?
non-
Identify the group arrangements on the molecule
Identify the branched substituent
isopropyl
A 10 carbon alkane would have what prefex?
dec-
Why are lower molecular weight alkanes more volatile than higher molecular weight alkanes?
Longer alkanes stack more efficiently, have higher intermolecular forces/ london dispersion
Why would isobutane have a lower boiling point than butane?
Isobutane is branched so it is less efficient at stacking than butane and has less intermolecular forces
Match the boiling points for propane, butane, and 2-methylpropane, -42C, -12C, -1C
Propane: -42C
Butane:-1C
2-methylpropane:-12C
Butane has the highest because it has a higher molecular weight and it is not a branched structure. 2-Methylpropane is branched so it is lower than butane. Propane is the lowest because it is the smallest.
True or False: alkanes are reactive in acid base chemistry
false, they are unreactive
How do you make an alkyl halide?
You get your halogen like Cl2, expose it to UV light to break the Cl and make a free radical. Add an alkane to the mixture and the halogen will replace an H at the end of the alkane.
Or- Hydrohalogenation where you add a halogen to the double bond of an alkene
True or False: alky halides are not reactive
FALSE!
Why are alkyl halides reactive
Halogens make GREAT leaving groups. THe haldes draw the electron density towards them leaving the carbon their bonded to electron deficient and a good place for nucleophilic attack
True or False: Alkenes tend to act as nucleophiles
True
True or False: Alkenes and alkynes are unreactive
False, they are reactive especially compared to alkanes
What does hydrogenation do to alkenes and alkynes?
It reduces them
What can you use to hydrogenate an alkene?
Pt or Ni
True or False: decreasing carbon-nitrogen or carbon-sulfur bonds results in reduction
True, a decrease in electronegative atoms can be considered reduction
Rank the following in order of increasing reactivity.
1,3,5-hexatriene
1-hexene
1,3-hexadiene
hexane
hexane
1-hexene
1,3-hexadiene
1,3,5-hexatriene
Hydrocarbon reactivity increases as electron density is increased. Double bonds increase electron density and so the more double bonds there are, the greater the reactivity will be.
