Topic 18.2 - Amines, Amides, Amino Acids and Proteins Flashcards
What is the amine functional group?
-NH2
How would you name CH3NH2?
Methylamine
How would you name CH3NHCH3?
Dimethylamine
How would you name CH3N(CH3)CH3
Trimethylamine
How would you name CH3CH(NH2)CH2CH3
2-aminobutane
If there are 2 or more functional groups what prefix do you use?
amino
How would you name NH2CH2COOH?
aminoethanoic acid
How would you name CH3CH2N(CH3)2?
dimethylethylamine
How would you name (CH3CH2CH2)2NH?
dipropylamine
How would you name the aromatic compound C6H5NH2?
phenylamine
Under what circumstances is the N-H peak broadened?
If there is large amounts of hydrogen intermolecular bonding
How would you name NH2CH2CH2NH2?
1,2-diaminoethane
What are the 3 way that aliphatic amines can be prepared?
- From halogenoalkanes
- From the reduction of nitriles (2 ways)
What are the conditions required to prepare an aliphatic amine from a halogenoalkane?
- Sealed flask
- excess ammonia in ethanol
What is the nucleophile in the preparationan aliphatic amine from a halogenoalkane?
NH3 (ammonia)
Draw and describe the mechanism for the preparation of ethylamine from bromoethane
- In the first step ammonia acts as a nucleophile. Ammonia attacks the delta + carbon that is attached to the delta - bromine. Draw an arrow from the lone pair of electrons on the NH3 to the delta+ carbon and another arrow from the C-Br bond to the Br.
- You begin the second stage with CH3CH2N(+)H3. In this stage ammonia acts as a base, a proton accepter, and attacks one of the hydrogen atoms on the N of the compound. Draw an arrow from the lone pair of electrons on the NH3 to the hydrogen atom and another arrow from the N-H bond of that hydrogen atom towards the +ve Nitrogen atom.
- Your final product should be CH3CH2NH2
Why is it important that ammonia is in excess in the preparation of aliphatic amines from halogenoalkanes? What would happen if it wasn’t?
This is because it is important that NH3 remains the nucleophile and so the major product is your primary amine. If the halogenoalkane was in excess then the NH2 on your product, that has a lone pair of electrons, can act as the nucleophile and so further substitutions will happen.
What type of reaction is the preparation of aliphatic amines from halogenoalkanes?
Nucleophilic substitution
What is a positive of preparing aliphatic amines from nitriles?
Both methods produce pure products
What is the reagent required for the preparation of aliphatic amines from hydrogenation of nitriles?
Hydrogen (H2)
What is the catalyst required for the preparation of aliphatic amines from hydrogenation of nitriles?
nickel
What is the equation for the preparation of aliphatic amines from hydrogenation of nitriles?
CH3CH2CH2CN + 2H2 -> CH3CH2CH2CH2NH2
What are the conditions required for the preparation of aliphatic amines from reduction of nitriles?
LiAlH4 in ethoxyethane, followed by dilute acid
What is the equation for the preparation of aliphatic amines from reduction of nitriles?
CH3CH2CH2CN + 4[H] -> CH3CH2CH2CH2NH2
What are the 2 reactions/steps in order in the process of preparing aromatic amines from benzene?
- Nitration
- Reduction
What are the reagents and conditions for the nitration step in preparation of aromatic amines from Benzene?
REAGENTS: Concentrated HNO3
CONDITIONS: Concentrated H2SO4, 50-60C
What do you produce from the nitration step in preparation of aromatic amines from Benzene?
Nitrobenzene
What are the conditions for the reduction step in preparation of aromatic amines from Benzene?
CONDITIONS:
- heat under reflux
- tin
- concentrated HCl
What is the equation for the reduction step in the preparation of aromatic amines form Benzene?
C6H5NO2 + 6[H] -> C6H5NH2 + 2H2O
Are amines soluble in water? If so, why?
Amines have an N-H bond with a lone pair of electrons on the Nitrogen atom. They are, therefore, able to form hydrogen bonds with water.
Why are amines basic?
As they have a lone pair of electrons on the nitrogen atom which means they are able to accept a proton
Write and equation to show the basic nature of ammonia
NH3 + H2O <-> NH4+ + OH-
Are Aliphatic amines strong or weak bases?
weak bases
Are Aliphatic amine stronger bases than ammonia?
Yes
Write an equation to show the basic nature of amines
CH3NH2 + H2O -> CH3NH3+ + OH-
what is the name of the ions that Amines for in water?
Alkylammonium ions
Draw and describe the mechanism of methylamine acting as base in water
- The lone pair of electrons on the nitrogen of methylamine attack one of the hydrogen atoms of water. The O-H bond breaks. Draw and arrow from the lone pair of electrons to the hydrogen atom and then another arrow from the O-H bond to the oxygen atom.
- Your products are CH3N(+)H3 and O(-)H
If an amine is a reasonably strong base then will its conjugate base be a strong or weak acid?
weak acid
What is the strength of an amine base governed by?
The availability of the lone pair of electrons on the nitrogen atom to accept a proton
Explain why methylamine is a stronger base then ammonia
Methylamine contains an alkyl group which is electron donating. This causes the electron density on the nitrogen atom to increase. Therefore the lone pair of electrons on the nitrogen atom is more readily available attract protons.
Explain why basicity increases as you increase carbon chain length of the amine
The longer the alkyl group the more electron donating it is. Therefore, as you increase the length of the alkyl group you increase the electro density on the nitrogen atom. Therefore the lone pair of electrons is even more readily available to attract a proton.
Why are aryl amines e.g phenylamine, very weak bases comparative to aliphatic amines and ammonia?
In aryl amines the lone pair of electrons on the nitrogen atom is incorporated into the delocalised ring. Therefore, the electron density of the delocalised ring increases but the electron density on the nitrogen atom decreases. Therefore, the lone pair of electrons is less readily available to attract protons.
Are amines more or less soluble in HCl than water? Why?
Amines are more soluble in HCl as they are bases
Write the equation for the reaction of butylamine with HCl
C4H9NH2 + HCl -> C4H9NH3+Cl-
What is the name of the ionic slat you produce in the reaction of butylamine with HCl?
butylammonium chloride
What smell do amines have?
A fishy smell
When does the fishy smell of amines disappear?
When HCl is added
Write the equation for the reaction of butylammonium chloride with sodium hydroxide solution
C4H9NH3+ + OH- -> C4H9NH2 + H2O
Why does sodium hydroxide solution remove a proton from an alkylammonium chloride salt?
As sodium hydroxide is a stronger base
Write an equation for the reaction of the gaseous amine ethylamine with HCl
CH3CH2NH2 + HCl -> CH3CH2NH3+Cl-
Amine + Acyl chloride ->…
amide
Amines and Acyl chlorides react..
vigorously
What us the functional group of amides?
C(O)NH
What do amines act as when they react with acyl chlorides?
nucleophiles
What is the type of reaction between acyl chlorides and amines?
Nucleophilic addition-elimination
What is the general name of the amide produced from the reaction of acyl chlorides with amines ?
N - substituted amide
Describe and draw the mechanism for the reaction of the Amine methylamine with the acyl chloride ethanoyl chloride?
- Ethanoyl chloride will have a delta + on the carbon attached to the Oxygen and Chlorine atom. The oxygen and chlorine atom will both have a delta -. The oxygen atom has 2 lone pairs of electrons that you also need to draw. methylamine is the nucleophile which attacks the delta+ carbon of ethanoyl chloride. Draw an arrow from the lone pair of electrons on the Nitrogen atom of methylamine to the delta + carbon. Draw an arrow from one of the bonds in the C=O bond to the oxygen atom.
- You begin this step with CH3CO(-)ClN(+)H2CH3. The oxygen atom has a negative charge and and the nitrogen atom has a positive charge. The oxygen atom also only has one lone pair of electrons now. Draw an arrow from the lone pair of electrons on the oxygen atom back into the C-O bon dot make it a C=O bond again and remove the negative charge on the oxygen atom. Draw an arrow from the C-Cl bond to the Cl atom.
- You begin this step with CH3CON(+)H2CH3. The Cl atom that you removed has a lone pair of electrons and a negative charge. It attacks one of the nitrogens hydrogens. Draw an arrow from the lone pair of electrons on the chlorine ion to the hydrogen of the nitrogen. Draw and arrow from the N-H bond to the nitrogen atom to get rid of its positive charge.
- Your products should be CHCONHCH3 + HCl/ N-mehtlyethanamide + hydrochloric acid
What are the 2 products of the reaction of acyl chlorides with amines?
N - substituted amide and HCl
How do you name N-substituted amides?
Start with N-
Amine -> first part of the name
e.g methylamine -> methyl
Acyl chloride -> second part of name
e.g Butyl chloride -> Butanamide
What do amines act as when they react with halogenoalkanes?
nucleophiles
Describe and draw the mechanism for the reaction of bromomethane with butylamine to form the secondary amine
- The lone pair of electrons of the N-atom of the butyl amine attacks the partially + C-atom of bromomethane. Draw an arrow from the lone pair of electrons on the N-atom to the C-atom. Draw a delta + on the C-atom and a delta - on the Br-atom of the bromomethane. The attacking of the amine nucleophile removes the Br-atom from the bromomethane. Draw an arrow from the C-Br bond of bromomethane to the Br-atom.
- In this step you begin with C4H9N(+)H2CH3, the N-atom has a positive charge as it has formed 4 bonds, and a bromine ion with a negative charge.One of the N-H bonds breaks and the electrons return to the N-atom. Draw an arrow from the N-H bond to the N-atom.
- You have formed the secondary amine Butylmethylamine, C4H9NHCH3, and Her
Why does the reaction of a primary amine with a halogenoalkane not stop after producing a secondary amine, assuming the halogenoalkane is in excesss?
This is because , the secondary amine that is produced from the first nucleophilic substitution is a stronger nucleophile than a primary amine. Therefore, you have a nucleophilic substitution from a secondary amine-> tertiary amine and then tertiary amine -> quaternary ammonium salt.
Describe and draw the reaction for the final substitution that can happen if bromomethane is added in excess to butylamine
- The lone pair of electrons on the tertiary amine, butyldimethylamine, attacks the C-atom of the bromomethane with a partially + charge. Draw an arrow from the lone pair of electrons on the N-atom to the C-atom. Draw a delta + on the C-atom and a delta - on the Br-atom. As the nucleophile attacks the delta + carbon the C-Br bond breaks. Draw an arrow from the C-Br bond to the Br atom.
- You have now created your quaternary ammonium salt, Butyltrimethylammoniumbromide. The N atom of the salt has a positive charge and this can’t be removed as the N-atom is not bonded to any hydrogens. You draw the salt with a + Br- on the side.
What is the major product when you use an excess of halogenoalkane in the reaction of halogenoalkane + primary amine?
Quaternary ammonium salt
What is the major product when you use an excess of primary amine in the reaction of halogenoalkane + primary amine? Why?
Secondary amine - there is more chance for the primary amine to continue acting as the nucleophile
Do amines make good ligands? Why?
Yes, due to the lone pair of electrons on the N-atom which can form dative covalent bonds
Write the protonation reaction and then the ligand exchange reaction for the formation of a complex ion from [Cu(H2O)6]2+ + 2C2H5NH2
PROTONATION
[Cu(H2O)6]2+ (aq) + 2C2H5NH2 (aq) -> [Cu(H2O)4(OH)2] (s) + 2C2H5NH3+ (aq)
- The amine removes H+ from 2 of the water molecules
LIGAND EXCHANGE
- ONLY HAPPENS on addition of excess ethylamine
[Cu(H2O)4(OH)2] (s) + 4C2H5NH2 (aq) -> [Cu(C2H5NH2)4(H2O)2]2+ + 4H2O (l)
In what case is the amide and N-substituted amide?
if the N-atom is attached to an alkyl group
What reaction produces amides?
Acyl chloride + Ammonia -> amide + hydrogen halide
What reaction produces N-substituted amides?
Acyl Chloride + Amine + hydrogen halide
What 2 functional groups does an amino acid have?
Carboxyl (COOH)
Amino (NH2)
How do you name amino acids?
- Find the longest carbon chain with the carboxyl, COOH, group in it and write down its name, the carboxylic acid
- Number the carbon atoms on the chain starting with the carbon of the carboxyl group being 1
- Write down the position of any NH2 groups and show that they are NH2 groups with ‘amino’. NB: you will always have 2-amino
- Write down the name of any other functional groups and say which carbon they are on
What is the general structure of amino acids?
NH2CH(R)COOH
What is the only part of amino acids that changes?
The R group
Are amino acids chiral? What are the exceptions?
Yes, they all have at least one chiral carbon EXCEPT Glycine (2-aminoethanoic acid) as its R group is -H.
What is the name for the amino acid CH3CH(NH2)COOH?
2-aminopropanoic acid
What is the name for the amino acid HOOCCH2CH2CH(NH2)COOH?
2-aminopentanedioic acid
What is the structural/skeletal formula for the amino acid 2-amino-3-phenylpropanoic acid?
C6H5CH2CH(NH2)COOH
What is the structural/skeletal formula for the amino acid 2-aminobutanedioic acid?
HOOCCH2CH(NH2)COOH
What is the definition of a zwitterion?
An ion with both a positive and a negative charge
What is the definition of the isoelectric point?
The pH value at which an amino acid exists as a zwitterion
What happens when an amino acid is in an aqueous solution of its isoelectric point?
The carboxyl group acts as an acid, a proton donater, and the amino group acts as a base, a proton accepter. Therefore, the H is removed from the O-H of the COOH group and is gained by the N atom of the NH2 group. This forms COO- and NH3+
What happens to the zwitterion when it is put into more alkaline conditions?
Alkaline conditions mean that there are an excess of OH- ions. These remove the extra H from the NH3+ forming the negative charged ion NH2CH(R)COO-
What happens to the zwitterion when it is put into more acidic conditions?
Acidic conditions mean that there are an excess of H+ ions. These attack the negatively charged COO- to form COOH. The final formed positively charged ion is NH3+CH(R)COOH
Why do different amino acids have different isoelectric points?
As they have different R groups
What are the products of the reaction dilute HCl and 2-aminopropanoic acid?
CH3CH(NH3+)COOH +Cl-
What are the products of the reaction dilute NaOH and 2-aminopropanoic acid?
CH3CH(NH2)COO-Na- +H2O
If an amino acid has an NH2 group as part of its R group, will that also act as a base and become NH3+?
Yes
In what states are amino acids zwitterions?
aqueous and solid
Do amino acids have high melting and boiling points? Why?
Yes, as they are crystalline solids that form strong ionic attractions between one ion and its neighbours. These strong ionic attractions are much stronger than hydrogen bonds so require more energy to overcome. Therefore, amino acids have high melting and boiling points in comparison to other molecules of a similar size.
What is the definition of a condensation reaction?
When a water/ small molecule is formed alongside the polymer
What are Proteins?
Condensation polymers of amino acids joined together by peptide bonds (amide functional group)
When amino acids are joined together what is removed from the COOH group and what is removed form the NH2 group?
COOH - OH
NH2 - H
this forms H2O
What generally is formed from the condensation reaction of 2 amino acids?
A dipeptide + H2O
What are the reagents and conditions for the first step of hydrolysing a protein?
REAGANTS: Concentrated HCl
CONDITIONS: Heat under Reflux
What do you need to add for the second step of hydrolysing a protein?
Water
Write the 2 equations for the hydrolysis of the peptide CH3CH(NH2)CONHCH2COOH
CH3CH(NH2)CONHCH2COOH -> CH3CH(NH3+)COOH + CH2(NH3+)COOH
CH3CH(NH3+)COOH + CH2(NH3+)COOH -> CH3CH(NH2)COOH + CH2(NH2)COOH
What is useful about the hydrolysis of peptides?
The products are the 2 amino acids that were used to make the dipeptide
After the hydrolysis of a peptide what is the method you use to separate and identify the amino acids present in the solution?
Paper Chromatography with Ninhydrin as a locating agent
What are the 2 differences between Addition polymerisation and Condensation polymerisation?
CONDENSATION POLYMERISATION
- You produce a polymer and water/small molecule
- From diCOOH, diol, diamine etc
ADDITION POLYMERISATION
- You produce the polymer ONLY
- From alkene
What groups react together to form polyamides?
diCOOH + diNH2
OR
diNH2 + diCOCl
What are the differences between the formation of polyamides form diCOOH and diamines versus diNH2 and diCOCl?
The reaction of diCOCl and diNH2 is much faster than the other, however, it produces HCl so in general the reaction of diCOOH and diNH2 is preferred.
Draw the repeat unit and other product for the reaction of diethanoic acid with ethane-1-2diamine
[-COCONHCH2CH2NH-] + 2nH2O
Can amino acids act as buffers in solution?
Yes
