10 Amines Flashcards
Define ‘amine.’
organic derivative of ammonia in which one or more hydrogen atom is replaced with alkyl or aromatic groups
What makes amines both basic and nucleophilic?
the nitrogen atom with a lone pair of electrons on the ammonia group
What do amines occur in?
both plants and animals
State 3 examples of amines and identify them as primary or secondary.
NH₃ (primary)
CH₃NH₂ (secondary)
CH₃NHH₃C (secondary)
(see document for full structures)
Draw and name two examples of neurotransmitters which are amines and state their role.
(i.e. found in the brain)
dopamine (double-ringed) and serotonin
an essential role in brain chemistry
(see document for structures)
Draw and name an example of a hormone which is an amine and state its role.
(Hint = can we go back to…)
(Hint for structure = 3x the normal needed for response)
adrenaline (now called epinephrine)
triggers fight-or-flight response to stress
(see document for structures )
Draw and name four examples of alkaloids which are amines and state their roles and state the R-groups differ between two of them.
(Hint = 2 heavy pain-relief drugs and 2 available OTC & in shops)
(Hint = one found in drink with 2Os)
morphine and codeine For morphine R = H and for codeine R = CH₃ plant products used as synthetic drugs nicotine and caffeine act as stimulants (see document for structures)
Describe the bonding in a nitrogen atom and state what it is similar to using a diagram.
(Hint: 3 bonds)
3 single bonds and 1 lone pair
bonding in N is similar to that in ammonia
(see document for diagram)
Describe the bonding in aliphatic amines.
N is sp3 hybridised
C-N σ-bond is formed by the overlap of nitrogen sp3 and carbon sp3 orbitals
What is the C=N=C bond angle? (Hint: tetrahedral angle with further repulsion)
~ 107°
Describe the bonding in aromatic amines using a diagram.
Hint: benzene and 2 p-orbitals and 2 bonds
N is sp2 hybridised
lone pair occupies the p-orbital and is delocalised
(see document for diagram)
State, through definitions, how an amine is classified as:
a) primary (1°)
b) secondary (2°)
c) tertiary (3°)
a) one alkyl/aryl group is bonded to the nitrogen atom
b) two alkyl/aryl groups as substituents
c) three alkyl/aryl groups as substituents
Draw and classify as 1°, 2° or 3°:
a) trimethylamine
b) methylamine
c) dimethylamine
a) 3°
b) 1°
c) 2°
(see document for diagrams)
State the general IUPAC process of naming amines.
amines are named as alkanamines
the -e in alkane name of the largest chain is changed to amine
State the IUPAC process of naming secondary amines.
the longest carbon chain names the amine
the other alkyl groups are listed in alphabetical order as prefixes as N-alkyl groups
What are the common names of amines and how often are they used?
non-standard names are used more frequently than IUPAC
e.g. alkylamine, not alkaneamine; aniline not phenylalanine
For longer alkyl chains or more complex molecules, which prefix is used and what for?
the prefix amino-
to indicate the functional group
For the following primary amines state the IUPAC name, the common name and draw the structures:
a) CH₃CH₂CH₂NH₂CH₃
b) CH₃CH₂CH₂CH₂CH(NH₂)CH₃
a) (3C alkane = propanone) IUPAC name = propanamine Common name = N-propylamine b) IUPAC name = hexan-2-amine Common name = 2-amino hexane (see document for drawings)
Name the amine shown on the document in stages.
1 - find the longest chain and identify the corresponding alkane. Generate the amine name = propanamine
2 - identify the smaller alkyl groups attached to the nitrogen = methyl, ethyl
prefix the amine name with the names of the smaller alkyl groups listed in alphabetical order, each prefixed with N
You get N-ethyl-N-methyl-propanamine
In terms of physical properties, how soluble are amines and why?
low molecular weight, amines are generally soluble
also soluble in organic solvents
In terms of physical properties, what are the general boiling points of amines and why?
boiling points are relatively high
they are higher than alkanes but primary and secondary amines have lower boiling points than alcohols of similar mass
In terms of physical properties, what are the characteristic odours of some amines and why?
some low molecular weight amines have sharp, penetrating smells similar to ammonia
higher molecular weight amines are often found in decaying animal tissues
Which amines are responsible for the smell of rotting fish?
low molecular-weight amines
Where are higher molecular weight (Mr) amines often found?
in decaying animal tissues
Explain how hydrogen-bonding occurs in amines.
lone pair of electrons on N are hydrogen-bond acceptors
N-H bond in primary and secondary amines = H-bond donors
How many hydrogen bonds can:
a) a primary amine form
b) a secondary amine form
c) a tertiary amine form
a) up to 3 H bonds
b) up to 2 H bonds
c) usually form 0 H bonds
What is the only molecule that is the exception to tertiary amines forming 0 H-bonds and why?
water
only water is small enough to avoid steric hindrance here
Draw hydrogen bonds between primary, secondary amines and water molecules (including lone pairs).
see document
In terms of the chemical properties of amines, what are amines a type of and how?
weak organic bases
accept H⁺
Because of the chemical properties of amines what do they produce when reacted with acids or water?
alkylammonium salts
Finish the following general reaction between an tertiary amine and water on the document drawing out structures with correct bond types (on document).
see document for answer
How are salts of amines named?
salts of amines are named by changing “amine” to “ammonium”
Name the salt formed when trimethylamine reacts with water.
trimethylammonium hydroxide
In terms of chemical properties, what does the formation of salts change?
change solubility, stability and crystallisation
How can the change in chemical properties during the formation of salts be used?
in pharmaceutical calculations
What is adderall and what is it made up of?
ASSS
CNS stimulant used in the treatment of attention deficit hyperactivity disorder and narcolepsy 25% Amphetamine aspartate monohydrate 25% Amphetamine sulfate 25% Dextroamphetamine sulfate 25% Dextroamphetamine saccharate
Draw out the chemical structure of Adderall.
see document for this
State how primary amines are chemically synthesised by ‘reduction of nitro compounds’ including:
a) reagents
b) conditions
c) the general reaction equation
(Hint: N”O₂”)
(Ar = alkyl)
a) Ar-NO₂
b) H₂, transition metal catalyst (i.e. Ni, Pt, Pd)
(Hint: N”O₂”= transiti”O”n metal catalyst)
c) Ar-NO₂ → ArNH₂
State how primary amines are chemically synthesised by ‘reduction of nitriles’ including:
a) reagents
b) conditions
c) the general reaction equation
(Hint = “Ni”trile compound)
a) RC≡N
b) H₂, Ni catalyst
c) RC≡N → RC-NH₂
State how primary, secondary and tertiary amines are chemically synthesised by ‘reduction of amides’ including:
a) reagents
b) conditions
c) the general reaction equation
(Hint = not counted as an O)
a) RC=ON(R’’)(R’)
b) LiAlH₄
c) (see document for this)
State how primary amines are chemically synthesised by ‘Hoffman degradation of amides’ including:
a) reagents
b) conditions
c) the general reaction equation
a) RC=ONH₂
b) KOBr
c) RC=O-NH₂ → R-NH₂
Provide the reaction for primary amines to be produced from alcohols in industry. State:
a) reagents
b) conditions
c) the general reaction equation (draw out too)
a) alcohol and ammonia
b) High temperature and high pressure
c) ROH + NH₃ → R-NH₂ + H₂O (see document for diagrams)
In the lab, what can alkyl halides be used as and how often are they used synthetically?
an alkylating agent
not often used synthetically, as the reaction is difficult to control
Draw out the general reaction equation for alkylamines production from an alkyl halide.
see document for this
Describe the properties of the lone pair of electrons ammonia molecule and explain why they are present.
(Hint: charge on N atom)
electron-rich/basic:
electron-pair donor
H⁺ acceptor
nucleophilic (-):
react with centres of positive charge
Provide the reaction for ‘condensation’ with carbonyls. State:
a) reagents
b) the general reaction equation (draw out too)
c) state the functional group created
d) state the type of base created
a) NH₃
b) R(R’)C=O → R(R’)=NH
(see document for diagram)
c) imine (=NH)
d) schiff base (with imine group)
Provide the reaction for ‘reductive amination’ of carbonyls. State:
a) reagents
b) the 3 different types of conditions
c) the general reaction equation (draw out too)
(Hint: carb”O”nyls)
a) NH₃, H₂ OR NaBH₃CN OR NaBH(OAc)₃ b) transition metal catalyst c) R(R')C=O → R₂C-NH₂
What is the chemical importance of reductive amination of aldehydes/ketones?
synthesis of primary, secondary and tertiary amines
State the biological importance of condensation with carbonyls in nitrogen metabolism drawing out the multi-stage example including enzymes.
NH₄⁺ + α-ketoglutarate + amino acid (NADPH₂, glutamate dehydrogenase) → glutamate (NH₃, ATP, glutamine synthetase) → glutamine
(see document for structures)
State the biological importance of condensation with carbonyls in the transfer of NH₂ groups drawing out the example including enzymes.
glutamate + keto-acid → α-keto glutarate + amino acid
(aminotransferase)
(see document for structures)
State the biological importance of condensation with carbonyls in enzyme mechanisms drawing out the example including enzymes.
pyridoxal phosphate-dependent enznymes, photosynthesis
pyridoxal phosphate → enzyme
(see document for structures)
State the products of the following general ‘acid-base’ reaction and state what the amine group acts as. (draw out on document too)
RR’R”N: + H-A ⇌
(Hint: split reagents 2 into positive and negative ions)
amine = base
RR’R”N: + H-A ⇌ RR’R”NH⁺A- + H-A
(see document for equation)
State the products of the following general ‘alkylation’ reaction and state what the amine group acts as. (see document for reaction)
(Hint: split reagents 2 into positive and negative ions)
amine = nucleophile
see document for equation
State the products of the following general ‘acylation’ reaction and state what the amine group acts as. (see document for reaction):
HO₂C-C(CH₃)-NH₂ + RC=OCl →
(Hint: split reagents 2 into positive and negative ions)
amine = nucleophile
see document for equation
Give a biological example of an ‘acylation’ reaction and state the enzyme involved.
(see document for this)
State the general reaction for diazonium salt formation.
(see document for this)
What characteristic do aliphatic diazonium salts (R= alkyl) have and how do they compare with aromatic diazonium (R = Ar) salts; what does this mean?
aliphatic are very unstable
aromatic are more, stable
thus aromatic are more useful
Finish the following diagram for aromatic amine formation (on document)
see document
What is Hoffman elimination and what is it used for?
used to produce an alkene and a tertiary amine from a tertiary amine
used primarily as a method for the production of alkenes
Draw out the Hoffman elimination reaction stages.
see document
