organic 3 Flashcards
what is the amine functional group
C-NH2
what is the amide functional group
C double bond O -NH2
what is the amino acid functional group
amine+ carboxyl groups and hydrogen and R group attached to carbon
why are amines boiling points lower than alcohols
oxygen in hydroxyl group is more electronegative than nitrogen therefore the hydrogen bonding in amines is weaker as there is less attraction between the nitrogen and hydrogen
how many bonds with water can an amine make
3- one from nitrogen, 2 from hydrogens
why are amines classed as weak bases
they have a lone pair on the N which can accept protons to form a conjugate acid
methylamine + H+ = methylammonium ion
how do you increase the basicity of amines
add alkyl groups as they push electrons towards the nitrogen so they are able to accept more protons as higher electron density
how can amines be prepared
1) halogenoalkanes by nucleophilic substitution
2) nitriles by reduction
3) aromatic nitro compounds by reduction
haloalkane + ammonia reagents
excess NH3
nitrile + H2 reagents
nickel catalyst
aromatic nitro compound boil under reflux reagents
tin and conc HCl
reactions of amines
amine + water -> ammonium salt + OH-
amine + acid -> ammonium salt
amine + acyl chloride -> N substituted amide
amine + halogenoalkane -> secondary amine
how to make a polyamide from diacyl chloride and diamide
remove H from NH2 and one Cl to make HCl and connect molecules
what does amphoteric mean
reacts as an acid and a base
if you put an amino acid into basic solution, what will happen
carboxylic acid group deprotonates
if you put an amino acid into a theoretically neutral solution, what will happen
H+ from COOH group forms bond with lone pair on N of NH2 group. this forms a zwitterion, an ion with both a permanent positive and negative charge, although overall the compound is neutral
because amino acids are zwitterions, this gives them properties of…
high melting point solids
dissolve well in polar solvents
dissolve poorly in non polar solvents
what is the isoelectric point of an amino acid
the point at which an amino acid exists as a zwitterion in solution
what turns amino acid to an ester
ethanol with a few drops of sulfuric acid with warming
benzene properties
colourless liquid
boiling point 80
carcinogenic
delocalised electrons
what were the 4 problems with the Kekule structure of benzene
-benzene did not undergo addition reactions despite being unsaturated
-bond lengths were all the same
-carbons appear to be equivalent
-enthalpy of hydrogenation is too small
is the enthalpy of hydrogenation of benzene less or more exothermic than a cyclic alkane
less exothermic
what is resonance
the idea that the double bonds in benzene switch regularly to all merge together (pi ring)
how does the 1.5 bond structure explain Kekules problems
1- bonds less electron dense so less susceptible to attack by electrophiles
2- same length as all 1.5
3- bromines on different carbons aren’t isotopes
4- thermodynamically more stable due to resonance energy
why is benzene less reactive than alkenes
pi system less electron dense than a normal pi bond due to resonance
less susceptible to attack by electrophiles
combustion of benzene
usually incomplete
burns with a smoky flame due to high carbon to hydrogen ratio
hydrogenation of benzene
mix with hydrogen, heat under pressure with nickel catalyst
what is good about electrophilic substitution of benzene
preserves pi system therefore preserves stability, swaps H for something else
electrophilic substitution of benzene reagents conditions
add Cl2/Br2 and AlCl3 (halogen carrier)
nitration of benzene
heat under reflux at 50
conc nitric acid and conc sulfuric acid
what happens if temp goes over 50 in nitration of benzene
multiple substitutions will occur which is explosive
friedel crafts reaction of benzene
AlCl3 and C2H5Cl
anyhydrous conditions
CH3COCl and AlCl3
phenol properties
low solubility in water
weakly acidic
more reactive than benzene
reactivity of phenol
lone pair of electrons on O of OH delocalises into pi system, increasing electron density
more susceptible to electrophilic attack
acidity of phenol
pi system overlap with O increases polarity of OH bond making H more likely to dissociate
