Alkanes Flashcards
At room temperature, formulas CH4 to C4H10 are
Gases
At room temperature, formulas C5H12 to C16H34 are
Liquids
What is the general formula for alkanes?
CnH2n+2
Straight-chain isomers have
Higher bps and mps
Why do branched isomers have lower bps and mps?
They reduce SA, which decreases to weak IMFs
Nucleophiles are attracted to
Positive charges
What are nucleophiles?
Electron-rich species that are often negatively charged
Nucleophiles correlate with
Basicity
The stronger the base the
Stronger the nucleophile
Bases act as
Electron donors
Stronger nucleophiles are ones that have
More of a negative charge / strong base
In protic solvents, which are the better nucleophiles?
Larger ions
In aprotic solvents, nucleophilics are related to
Basicity
The best leaving groups are
Weaker bases
SN1 is
Unimolecular nucleophilic substitution
SN1 is associated with the formation of
Carbocation
How many steps are in SN1?
Two
What are the two steps of SN1?
- Dissociation of substrate molecule into carbocation and leaving group
- Combination of carbocation with nucleophiles to form substituted product
SN1 depends on the
Stability of carbocations
Which solvents are ideal for SN1?
Polar protic
SN1 reactions do not require
Strong nucleophiles
SN1 reactions produce
Racemic mixtures
SN2 is
Bimolecular nucleophilic substitution
How many steps are in SN2?
One
What happens during the SN2 reaction?
There is an attack from the back, forming a transition state
SN2 produces
Inversion
SN2 reactions require
Unhindered nucleophile
SN2 depends on the
Order of reactivity, with 1º being first
Which solvents are ideal for SN2?
Polar aprotic
What happens in Free Radical Substitutions?
One or more Hs are replaced by Halogens
What are the three steps of Free Radical Substitution?
- Initiation
- Propagation
- Termination
Initiation of Free Radical Substitution is when
Diatomic halogens are cleaved by ∆ or peroxides
Initiation of Free Radical Substitution forms
Free radicals that are extremely reactive
Propagation of Free Radical Substitution is when
A radical produces another radical
Propagation of Free Radical Substitution contains the
- Formation of HX and alkyl radical
- Alkyl radical reactions with X2
Termination of Free Radical Substitution is when
2 Free radicals combine to form molecule
Pyrolysis is when a molecule
Breaks by heat in absence of O2
Pyrolysis allows for
Radicals to recombine
Disproportionation is when
Radical transfers H atoms to another radical
