Chapter 27 - Amines, Amino Acids, Polymers Flashcards
1° amines?
have one alkyl chain attached to the N (so 2H too)
2° amines?
have 2 alkyl chains attached to the N (so 1 H)
3° amines?
have 3 alkyl chains (so no H) attached to the N
how to name short primary amines?
- alkyl prefix
- then add ending amine
how to name short secondary and tertiary amines?
- di/tri alkyl ➡ how many alkyl groups attached to the N
- amine ending
how to name longer amines?
- amino prefix
- name the rest of the chain as usual
benzene and an amine gr is?
phenylamine
pH of amines?
- 9/10
- weak alkaline
amines solubility?
- can bond w water
- weak IDFs between molecules, easy to overcome
as C chain length ⬆, the solubility of the amine ?
solubility ⬇ as C chain length ⬆ as IDFs increase so the organic molecule stays bonded together
ammonia + water reversible ➡
NH4+ + OH-
formation of ammonia?
N2(g) + 3H2 (g) RA 2NH3(g)
- the haber process
- Fe(s) catalyst
ammonia acting a base equation?
NH3 + H2O ➡ NH4+
When ammonia acts as a base?
ammonium salt formed
structure of ammonia?
pyramidal, 107°
structure of methylamine?
pyramidal, 107°around N
109.5°, tetrahedral around C
Amines also react with acids to ?
form ammonium salts
amine groups mean?
H bonds between molecules
phenylamine?
has higher e- density than benzene bc of NH2
neutralisation?
if there r 2 N, then 2 protons (H+) are added
aliphatic =
chains and rings but NOT benzene rings
aromatic =
benzene ring
preparation of 1° aliphatic amines?
R: DRY (to stop alcohol formation) NH3 in excess (to prevent further subs)
C: in ethanol, reflux
CH3Cl + 2NH3 ➡ CH3NH2 + NH4Cl
preparation of 1° aliphatic amines: why is ammonia left w + charge?
one e- from lone pair went to C in bond
how do we prepare aromatic amines?
reduction (addition of H) of nitrobenzene
preparation of aromatic amine 1?
R: Sn (tin) and conc HCl
C: reflux
Eq: nitrobenzene + 6[H] ➡ phenylamine + 2H2O
preparation of aromatic amine 2?
phenylamine + HCl ➡phenylammonium chloride salt (C6H5NH3Cl)
Reverse the reaction:
C6H5NH3Cl + NaOH ➡ phenylamine + NaCl + H2O
Further nucleophilic substitution: preparation of a secondary amine?
CH3Cl + 2NH3 ➡ CH3NH3 + NH4Cl
ammonia is NOT in excess
Further nucleophilic substitution: preparation of a tertiary amine?
react a secondary amine with CH3Cl
why can’t be use ammonia and benzene to make phenylamine?
- NH3 = nucleophile
- Benzene takes part in electrophilic reactions
- phenyl is e- dense, repels nucleophiles
NS to form an amine always also forms?
an ammonium salt
v
vv
v
v
how many optical isomers does a molecule with 2 chiral carbon atoms have?
4
features that allow a molecule to be described as an AA?
amine group AND CA group
in an alpha amino acid?
NH2 and COOH bonded to the same C
when an AA is in alkaline conditions?
both COOH lose their H+ and react w the metal ion e.g. COO-Na+
when an AA is in acidic conditions?
NH2 gains a H+ to become N+H3 and reacts w negative ion
ethanoic acid vs glycine: solubility and pH
Ethanoic acid: ph4, red, soluble as 1 layer
gly: neutral - 5/6 (fewer H+) - dissolved
NH2 and COOH almost cancel out
ethanoic acid vs glycine: + Mg
Ethanoic acid: squeaky pop, vigorous reaction
gly: green quickly, little fizzing, no squeaky pop
ethanoic acid vs glycine: indicator and NaOH
Ethanoic acid: low pH - more H+
gly: more alkaline, higher pH - less H+
ethanoic acid vs glycine: + Na2CO3
Ethanoic acid: fizzing, limewater bubbling
gly: blue, no fizzing
ethanoic acid vs glycine: ethanol and conc H2S04?
Ethanoic acid: fizzing, strong smell
gly: milder smell, fewer COOH as internal ionisation
AA: phenol FG is ?
acidic
AA: whatever O does in an organic compound,
sulfur does too
NH2 is?
the amine group
amino acids reactions?
- nucleophilic
* neutralisation
Amine neutralisation reaction
CH3NH2 + HCl ➡ CH3NH3+Cl-
amine nucleophilic substitution reaction?
CH3Cl + 2CH3NH2 ➡ (CH3)2NH + CH3HN3Cl
amide bond?
C=ONH
AA in acidic conditions?
NH2 ➡NH3+
reacts w basic part which becomes protonated
AA n alkaline conditions?
COOH loses H+ which reacts w OH- to form H2O
COO-
Remember ALL
acidic and all basic groups
phenol in alkaline conditions ?
loses H off OH, leaving O-
what gives rise to optical isomerism?
• The C atom in the centre has 4 different groups of atoms attached - this is a chiral carbon atom
CCA: CH2 and CH3
are different groups!
CCA: if the C only has 3 bonds (a double bond)
can’t be a CCA
CCA: non superimposable
- optical isomers are non superimposable mirror images bc they have different spatial arrangements
- these are optical isomers
the non-superimposable mirror images are called…
optical isomers or enantiomers. This type of molecule is said to be chiral.
what is a chiral C atom?
- C surrounded by 4 diff groups
- sometimes >1 in a molecule
- denoted by an *
what is the rule for determining whether an AA is classified as a D or L optical isomer?
if the AA rotates plane polarised light to the right it is D/+ (L/ - if left)
what type of AA are used in the human body?
always L/- isomer. Carbs are all D/+ isomer in the body.
similarities between optical isomers?
- very similar chemical and physical properties
* same structural and molecular formula (they are stereoisomers)
differences between optical isomers?
- they rotate plane polarised light in opposite directions
- they react differently w other chiral molecules
- different arrangement of atoms in space
optical isomerism is a type of?
stereoisomerism
amide FG?
C=ONH
When do amides occur?
when u react an acyl chloride w ammonia and amines
What is a condensation reaction?
joining 2 molecules together by removing a molecule of water
what are peptides?
- amides
* that form when 2 AAs react in a condensation reaction
dipeptides?
form when 2 amino acids react together
there can be ? in peptides?
chiral carbon atoms
peptide bond?
only used when joining 2 AA (an amide bond)
when the question asks for 2 (di)peptides?
just rearrange the order of the AA in the polyamide/ peptide
e.g. Cys-Ser and Ser-Cys
when naming a peptide…
just write the seq of AAs
⭐peptides
look out for rings, see if more condensation can happen. Examiner will often get u to form a ring and deduce the structure of the ring
hydrolysis of a peptide,
if acid/ base specified then include the ion in the products
⭐when hydrolysing peptides w an acid catalyst,
protonate ALL amine groups (even ones on the end!)
⭐when hydrolysing peptides w an alkali catalyst?
acid groups are deprotonated (lose H+) - be careful to check r group for acid
remember that phenol is an acid
alcohols are ?
neutral, OH stays as it is
which AA is optically inactive?
r group = H
when talking about the solubility of a peptide?
- talk about H bonds w water (NH2/COOH)
* talk about induced dipole forces - energy needed to break
how to determine if a peptide is basic/neutral/alkaline?
- how many acidic groups
- vs how many basic groups
- if there’s more basic, H+ would be accepted and alkaline pH
when can you form a polyester?
- when have dioic acid/ diol
* when have a molecule w CA and alcohol
suggest what makes a polymer biodegradable?
- ester bond can be hydrolysed by water in the envir
* C=O absorbs radiation
condensation reactions remove?
H2O/HCl
condensation polymerisation is just ? multiple times
esterification
condensation polymerisation put FG
at the end of the molecule
polyester - monomers?
- 1 monomer w alcohol and CA FG (2 of these used)
2. 2 monomers - 1 diol and 1 dioic acid
polyesters will have
more than 1 repeat unit
condensation polymerisation remember to put ? in equation
water
what is a diamine?
2 NH2 groups
how can a polyamide be formed?
- diamine and dicarboxylic acid
2. AAs
condensation polymerisation: CA loses
OH
condensation polymerisation: remember
lines either side of the polymer to show it repeats
condensation polymerisation: when benzene is involved, be careful to
keep the positions right
condensation polymerisation: benzene’s effect on the polymer
- benzene is planar, 120 degrees
- makes chain flat
- so pack closely together
- dense, strong IM and ⬆ MP
CP vs AP - biodegradable?
- polyalkenes do not biodegrade
* CP - polyesters and polyamides can be hydrolysed by H2O so are biodegradable
acid hydrolysis of polyesters?
• monomers reformed
base hydrolysis of polyesters?
- NaOH ➡ NaO and H
- NaO to C=O to make Na+ -OC=O
- H to O
base hydrolysis - need ? mol of base when a monomr has 2 CA groups?
2
acid hydrolysis of polyamides?
• NH2 protonated in acid to become NH3
Base hydrolysis of polyamides?
NaO to C=O and H to NH
when is an amide formed and when is a polyamide formed ?
amide: CA + Amine ➡ amide + water
polyamide: diol + dioic acid/ 2 AA
FOR POLYAMIDE IT HAS TO BE DI
how to tell if it’s an addition or condensation polymer?
Addition: backbone chain that only contains C
condensation: chain will contain ester/amide bonds - break these to get monomers
⭐phenol does NOT
form ester w CAs
when asked about a polymer impurity>
think abt rings
single headed arrow shows movement of?
1 electron. Used when radicals are formed
where do the numbers in the name of nylon come from?
the no. of Cs
first amine Cs then CA Cs
why can a polymer undergo acid hydrolysis but is not biodegrdable?
the backbone doesn’t break, only sidechain does so polymer not broken down
base hydrolysis n
2n-1 of the base
why do addition polymers not degrade easily?
- alkanes
* can’t be hydrolysed
properties of polymers involving benzene rings?
- flat molecules
- pi bond in C=O and 120 trig planar
- chains pack closely
- strong IMFs (H bonds bc amide group)
- dense structure
Ap: no. of types of monomer ?
1, alkenes
AP: atom economy?
100% - one product
AP: type of reaction?
electrophilic addition
AP: uses ?
- PVC
- Plastics
- Teflon
AP: biodegradability?
no - alkanes = unreactive
CP: no of type of monomer ?
- diamines and dioic acid
- dioic acid and diol
- AA
- hydroxy-oic acid
CP: atom economy?
<100% - water/ HCl formed
CP: type of reaction?
condensation
CP: uses?
- making polyester and polyamides
* often used as fibres and ester
CP: biodegradability?
yes amide bond can be hydrolysed using water from environment
