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32 Cards in this Set

  • Front
  • Back
What is a haloalkane?
A compound containing a halogen covalently bonded to an sp3 hybridized carbon atom.
Do halogens take greater naming preference than alkyl substituents in naming?
No. Whichever substituent will give you the lowest first number wins.
What are common names for haloalkanes?
Alkyl halides (ie. ethyl bromide).
What is a vinyl group?
CH2=CH-R
What is an allyl group?
CH2=CH-CH2-R
What is more electronegative carbon or halogens?
Halogens.
How does a halogen affect boiling point?
1. Branching decreases boiling point
2. For a haloalkane with same size and shape as alkane, haloalkane will have greater boiling point because of polarizability associated with the halogen group.
3. Flouroalkanes will have similar boiling point to alkanes of same size and shape because of the relatively small size of fluorine and low polarizability due to high electronegativity.
Will a larger or smaller halogen have greater polarizability?
Larger halogens.
What is polarizability a measure of?
Each of distortion of the distribution of electron density about an atom or group.
How does addition of a halogen affect density?
Density increases because of halogens large mass to volume ratio (remember atom size decreases from left to right so a fluorine though heaver is actually smaller than a carbon).
Which is a stronger bond CH or CX?
CH with the exception of CF.
How are bond strengths determined?
Through their bond dissociation energy, or the energy required to break the bond.
What is a radical?
A chemical species with one or more unpaired electrons.
How are radicals formed?
Through homeolytic cleavage such that each atom involved in a bond breaking receives one of the electrons.
What two halogens are commonly used in halogenation of an alkane?
Br2 and Cl2
What is needed for halogenation of an alkane even though it is neither a product nor reactant?
Heat or light.
What is regioselectivity?
The preference of one direction of chemical bond making or breaking over all other possible directions.
What type of carbon will a halogen most rapidly halogenate?
Tertiary > Secondary > Primary
Which chemical is more subject to regioselectivity bromine or chlorine?
Bromine
Will a more substituted carbon have higher or lower bond dissociation enthalpy than a lesser substituted carbon?
Lower because the carbocation formed will be more stable based on the the stabilization provided by substituents.
What are three steps in the halogenation of an alkane?
Initiation, propagation, termination.
What does chain initiation entail?
Formation of radicals from non-radical compounds.
What is the characteristic feature of chain propagation?
The formation of a new radical by the reaction of a radical and an uncharged molecule. This step can happen repeatedly.
What is chain termination and when does it occur?
It is destruction of radicals and it occurs when two radicals react to form a neutral species.
After initiation, what provides the energy for subsequent propagation?
The heat released from the reaction.
What is bromine regioselective for halogenation of alkanes?
Because chlorination occurs faster than bromination, it does not care as much about the stability of the carbon radical intermediate and therefore abstracts any available hydrogen.
What is the rate determining step in the halogenation of alkanes?
Abstraction of a hydrogen by a radical.
What is an allylic carbon?
A carbon next to a carbon=carbon double bond.
What is allylic halogenation?
Halogenating a carbon next to a carbon=carbon double bond.
At room temperature, will bromine the allylic carbon or the carbons of a double bond?
The carbons of the double bond.
At high temperatures will bromine attack the allylic carbon or carbons of the double bond?
The allylic carbon because more bromine radicals are available so they become less regioselective and will abstract hydrogens from a less substituted carbon.
What is autooxidation?
Air oxidation of materials such as unsaturated fatty acids.