Amines Flashcards
(13 cards)
Nomenclature
What do name an amine with a methyl group attached?
What do you call an anime with 2 methyl groups attached?
What doe you call an amine attached to a benzene ring?
What prefix do you use when molecule has an amine and other functional groups?
When do you use N-?
Methylamine Dimethylamine Phenylamine Amino To show the functional group is attached to the nitrogen of the amine
Physical properties
What phase are the early members of aliphatic amines?
What are their bpt compared to alcohols of similar chain length?why?
Why are shorter chains very soluble in water and ethanol?
Why are aromatic amines less volatile and virtually insoluble?
Gases or volatile liquids
Lower because the hydrogen bonding in them is weaker
Bc of hydrogen bonding
Because of the predominance of van der wals
Reactivity of amines
What does having a lone pair allow them to act as?(2)
What does the lone pair form bonds with to act as:
A base
A nucleophile
How reactive are they?
What are they useful as?
Base and nucleophile
H+ d+C
Very
Intermediates in synthesis
Nucleophillic properties
What are Lewis bases?
What are hydrogen atoms replaced with when reacted with haloalkane?
What is formed when haloalkane+ammonia?
How do you then produce a primary amine from this?
Draw two equations to represent this using CH3Br and NH3
Electron pair donors Alkyl groups Alkyl ammonium salt Proton exchange with another molecule CH3Br+NH3>CH3NH3+Br- CH3NH3+NH3>CH3NH2 + NH+Br-
Nucleophillic properties How is the primary amine further substituted? What does this form? Equations What does 3rd alkylation form? What does this then donate to form a tertiary amine? Equations What is the final outcome? What does this limit the usefulness of?
React primary amine with haloalkane Dialkylammonium salt CH3Br+CH3NH2>[(CH3)2NH2]+Br- [(CH3)2NH2]+Br- + NH3>[(CH3)2NH] + NH4+Br- Trialkylammonium salt Proton [(CH3)2NH] +CH3Br > [(CH3)3NH]+Br- [(CH3)3NH]+NH3 >[(CH3)3N] + NH4+Br- Mixture of products Direct alkylation
What do you use an excess of to gain a high yield of quaternary salt?
What does this encourage? Why?
What do you use to get a high yield of primary amine?
What does this discourage?
Haloalkane
Encourages further substitution
Plenty R groups available
Xs NH3
Further substitution
What is a primary,secondary and tertiary amine?
N with one,two,three alkyl groups
Draw out the first step mechanism for nucleophillic substitution
Second step mechanism
Idiot
Preparation
How do you prepare a primary aliphatic amine?(what do you heat the haloalkane with and what do you dissolve this in)
Equation for example of this?
What is the second method? What results and what do you do to this?
Equations
Heat haloalkane with xs ammonia dissolved in ethanol
CH3CH2Br+2NH3>CH3CH2NH2 + NH4+Br-
Heat haloalkane with KCN dissolved in ethanol then reduce the resulting nitrile
CH3CH2Br + CN- >CH3CH2CN + Br-
CH3CH2CN + 4[H+] > CH3CH2CH2NH2
What are quaternary ammonium salt with 2 long chain alkyl groups used as?
What are they used in?
Cationic surfactants
Fabric softners
Base properties
What are amines and ammonia in terms of bronsted-lowry acids and bases?
What is basicity of lone pair?
Equation for the formation of NH4+
Formation of RNH3+
What do they react with acids to form?
Example with RNH2 and HCl and name product
Example with phenylamine and HCl and name product
What does the strength of a base depend on?
Base Availability of the lone pair NH3 + H+ > NH4+ RNH2 + H+ > RNH3+ Ionic salt RNH2 + HCl > RNH3+ + Cl- Methylammoniumchloride C6H5NH2 + HCl > C6H5NH3+ + Cl- Phenylammoniumchloride How readily it accepts protons
What does lower pKa mean?
So what does higher pKa indicate?
Why is methylammine a stronger base than ammonia?
What is the alkyl group with regards to electrons?
Why is phenylamine is a weaker base than ammonia?
What is the Aryl group with regards to electrons?
Higher Ka > greater acid strength
Stronger base
Electron donating effect of the methyl group increases the availability of lone pair on N
Electron releasing
Benzene group decreases availability of the electron be they become involved in delocalised ring system
More electron withdrawing
Preparation
How do you get an aromatic amine?
What do you metal acid combo do you use?
Draw example equation
Reduction of aromatic nitro compounds
Sn/HCl
