17.5 Flashcards
what are amines
nitrogen containing compounds
explain the structure of an amine
3 bonding pairs with at least one alkyl group
1 lone pair
trigonal pyramidal shape
what is a primary amine
nitrogen is attached to 1 alkyl group
what is a secondary amine
nitrogen is attached to 2 alkyl groups
what is a tertiary amine
nitrogen is attached to 3 alkyl groups
whats the name of the compound C6H5NH2
phenylamine
what is the equation for the preparation of a primary amine from a halogenoalkane
CH3Cl + NH3 -> CH3NH2 + HCl
what is the equation for the preparation of a secondary amine from a halogenoalkane
CH3Cl + CH3NH2 -> (CH3)2NH + HCl
what are the 2 ways of forming amines from halogenoalkanes
heating with ammonia under pressure in a sealed container
or mix with aqueous ammonia
how does the formation of amines from halogenoalkanes involve and nucleophilic attack
lone pair on ammonia act as nucleophile and attack the electron deficient carbon, the amine formed then acts as a nucleophile and attacks another electron deficient carbon to form a secondary amine
how can the number of secondary amines being formed from the products of halogenoalkanes and ammonia be reduced
ammonia is used to excess so that it outnumbers the molecules of primary amines formed and some of the excess ammonia reacts with the HCl to form NH4Cl
what is the equation for the reduction of ethanenitrile
CH3CN + 4[H] -> CH3CH2NH2
what are the conditions and the reagent for the reduction of nitriles to primary amines
reducing agent - lithiumtetrahydridoaluminate
mixed in dry ether
why must the reduction of nitriles to primary amines be in dry ether
so that no water can affect the reaction
whats the equation for the reduction of nitrobenzene
C6H5NO2 + 6[H] -> C6H5NH2 + 2H2O
what are the reagents and conditions for reduction of nitrobenzene to phenylamine
reducing agent (tin) and concentrated hydrochloric acid
heated under reflux
how does phenylamine react with acids
forms phenyl ammonium ion (C6H5NH3+)
how can phenyl ammonium ion be converted back to phenylamine
added alkali (sodium hydroxide)
C6H5NH3+ + OH- -> C6H5NH2 + H2O
what are phenylamines commonly used for
dying blue jeans
manufacturing polymers
pharmaceuticals
what is the trend in solubility of primary aliphatic amines as hydrocarbon chain decreases
as hydrocarbon chain increases solubility decreases
why are amines soluble in water
their lone pair on the nitrogen allows them to form hydrogen bonds with the water molecules
how can amines act as a base when mixed with water
the nitrogen uses its lone pair to form a dative bond with the hydrogen on the water molecule
CH3NH2 + H2O <=> CH3NH3+ + OH-
how does ammonia act as a base when mixed with water
the nitrogen uses its lone pair to form a dative bond with the hydrogen on the water molecule
NH3 + H2O <=> NH4+ + OH-
what is basicity
the extent to which a base can donate a lone pair of electrons to the hydrogen atom of a water molecule
what is the trend is basicity of amines as the hydrocarbon chain length increases and why
basicity strength increases as chain length increases because the alkyl groups are electron-releasing so increase the density of the nitrogen and make it more open to donate its lone pair
is ammonia a stronger or weaker base than alkylamines
weaker
is phenyl amine a strong or weak base and why
weak base because the lone pair on the nitrogen are attracted to the delocalized pi bond making the nitrogen less electron rich and making the lone pair less available for donating
how do amines react with acids
they all react with strong acids to form ionic salts
what is the equation for the reaction between methylamine and nitric acid
CH3NH2 + HNO3 -> CH3NH3+ + NO3-
what is the equation for the reaction between butylamine and hydrochloric acid
CH3CH2CH2CH2NH2 + HCl -> CH2CH2CH2CH2NH3+ + Cl-
what is an addition-elimination reaction
occurs when 2 molecules join together, followed by the loss of a small molecule
what is an amide
carbonyl group next to a NH group
why do amines react with halogenoalkanes and what is produced
the electron deficient carbon reacts with the electron rich nitrogen to form a secondary amine a hydrogen halide
what is the equation for the reaction between butylamine and chloroethane
CH3CH2CH2CH2NH2 + CH3CH2Cl -> CH3CH2CH2CH2NHCH2CH3 + HCl
what happens if the products of the reaction between a halogenoalkane and alkylamine react further
the secondary amine will react with the halogenoalkane and form a tertiary amine and a halogen ion
what is a quaternary ammonium salt
an ammonium ion in which all of the hydrogens have been replaced by alkyl groups
why is reacting amines with halogenoalkanes not a good way of preparing primary/secondary/ tertiary amines
because the product gives a mixture of similar products
give a use on quaternary ammonium salts
fabric softener
what is the equation for the reaction of ammonia with hexaaquacopper(II)
[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4(H2O)2]2+ + 4H2O
what will be observed when an amine reacts with hexaaquacopper(II)
first a blue precipitate will form then as the amine is added in excess it will dissolve and a deep blue solution will form
what is the functional group of an amide
carbonyl group joined to an amino group
CONH2
what are the properties of amides
solids
lower aliphatic amides are soluble
low mp & bp
why are lower aliphatic amides soluble
because the central carbon atom is attached to an oxygen and a nitrogen which are very electronegative so the bonds are polar and have lone pairs which help to form hydrogen bonds with water
what two molecules form a polyamide
a dicarboxylic acid and a diamine
draw the structure of an amino acid
what is the isoelectric point
the pH of an aqueous solution in which it is neutral
what is a zwitterion
a molecule containing positive and negative charges but which have no overall charge
are amino acids soluble
yes
what is the equation for an amino acid acting as a base
H2NCHRCOOH + H2O <=> H3N+CHRCOOH + OH-
what is the equation for an amino acid acting as an acid
H2NCHRCOOH + H2O <=> H2NCHRCOO- + H3O+
what does the isoelectric point tell you about the acidity or alkalinity of a zwitterion
low isoelectric point = predominantly acidic
high isoelectric point = predominantly basic
are amino acids optically active
yes except glycine
what is a peptide bond
the bond formed by a condensation reaction between the carbonyl group of one amino acid and the amino group of another amino acid
what type of reaction occurs when two amino acids react together
acid-base reaction
what is the difference between a long-chain polypeptide and a protein
proteins have more complex 3D structures, primary. secondary, tertiary, quaternary
how can a protein be broken down into their individual amino acids
heat with concentrated HCl to break peptide bond
how can chromatography be carried out on proteins to identify amino acids
hydrolyse a protein so a mixture of amino acids is produced, spot the protein on chromatography paper and using a suitable solvent the individual amino acids will rise to different heights however amino acids are colourless so the chromatogram must be prayed with a developing agent (ninhydrin) so that the position of the amino acids can be seen
what developing agent is used for the chromatography of amino acids
ninhydrin
why is ninhydrin not used often
it is toxin
