Organic Synthesis, Aromantic Chemistry, Polymers, Amino Acids Flashcards
(101 cards)
1
Q
Comparing Base Strengths (Amines)
A
- The strength of a base is dependent on the availability of the lone pair and its ability to pick up protons
for amines
- The greater the electron density in the Nitrogen atom, the better it can pick up protons ∴ the better the base
- this is dependent on the groups attached to the nitrogen.
2
Q
Preparation of Aromatic Amines
A
- Aromatic amines are formed through the reduction of nitro aromatic compounds e.g nitrobenzene
- aromatic amines are very important for the manufacture of dyes
methods to reduce nitrobenzene:
tin and concentrated hydrochloric acid
- heat a mixture of nitrobenzene, tin and conc HCl under reflux
- form phenylammonium chloride which is soluble in water
- add a base e.g NaOH to produce phenylamine, which is insoluble in water
hydrogen and metal catalyst (platinum or nickel)
3
Q
Nucleophilic Substitution with Halogenalkanes
A
Reagents:
Aqueous, alcoholic ammonia
Conditions:
Reflux, aqueous alcoholic solution under pressure
- the product is dependent on whether the halogenoalkane or ammonia is in excess
- If ammonia is largely in excess then a primary amine will be formed
- If the halogenoalkane is an excess then the reaction with continue until a quaternary ammonium salt is formed as the amine replaces the rest of it’s hydrogens
USE:
- very rarely use this method to synthesise amines because it is very difficult to control
4
Q
Properties of Amines
A
Boiling Point -
- High boiling points
- due to the intermolecular forces (hydrogen bonding: N-H)
Structure -
Pyramidal
- 107°/107.5°
- due to the repulsion of the lone pairs
Solubility -
- soluble (somewhat) due to the polarity of the bonds
- solubility decreases as the molecules get heavier
- lower mass compounds are soluble in water due to polarity
- soluble in organic solvents (except aromatic amines due to the benzene ring)
- Lewis Bases
- Bronsted-Lawry Bases
- Nucleophiles
( amines act as both bases and nucleophiles, the more soluble the amine, the better it is at being a base)
5
Q
What is a Lewis Base
A
- A molecule that can donate a lone pair
- Amines can acts as Lewis Bases
6
Q
Order of Base Strengths and Why
A
strongest -> weakest:
secondary, primary, ammonia, aromatic
- electron releasing substituents (i.e CH3 groups) increase the basicity as the electron density is increased so the lone pair is more effective.
- this is the positive inductive effect
- electron withdrawing substituents (i.e benzene rings) decrease basicity as the electron density on N is lowered due to the electron density of e.g a benzene ring, by taking the lone pairs and delocalising them, making the lone pair less effective.
7
Q
Why does phenylamine form oily drops when in water?
What would happen if you added conc HCl?
What would happen if you then added NaOH and why?
A
- Phenylamine is not very soluble in water, this is due to the benzene ring being very stable and unreactive
- the acid will cause the phenylamine to dissolve
- the proton donated will turn it in to an ammonium ion
- adding NaOH will cause the oily drops to reform
- this is because it goes back to its amine structure rather than it’s ionic structure
8
Q
Reduction of Nitriles (provide a general example)
A
- both methods produce a primary amine
- Reduction using LiAlH4 in Dilute Acid
- Reduction using Hydrogen + Nickel (or other metals) catalyst
-High Temp, High Pressure
9
Q
Advantages and Disadvantages of Aliphatic Amine synthesis methods
A
10
Q
Quaternary Ammonium Salts
A
- quaternary ammonium salts with long hydrocarbon chains are used as cationic surfactants in fabric conditioners/softners and hair softeners
- This is due to the positive cationic head that is attracted to the negatively charged fibres or protein sites on hair molecules/ fabric
material molecules, which reduces static charge, making them softer
11
Q
Why is Nucleophilic substitution with amines so hard to control?
A
- this is due to the continuous further substitutions that occur during to the amines
e.g
bromoethane + ammonia
- first it forms a primary amine, ethylamine
- ethylamine can also act as a nucleophile so substitution occurs again
- a secondary amine is then formed but that can also go under substitution
- and this continuous until a quaternary ammonium salt is formed
- reaction ends here because there is no lone pairs available to use anymore
12
Q
Carboxylic Acid Formation using Nitriles
A
- carboxylic acids can be formed from the hydrolysis of nitriles
- nitrile is made to react with hydrochloric acid under reflux to form a carboxylic acid and ammonium chloride salt.
13
Q
Name 3 reactions for which condensation polymers are formed
A
- dicarboxylic acids and diols = polyester
- dicarboxylic acids and diamines =
polyamide - amino acids = polypeptide
14
Q
Define Condensation Polymerisation
A
- Condensation Polymerisation is where 2 different monomers with at least 2 functional groups react together
- when they react a link is made, and water/a small molecule is eliminated
15
Q
What is the importance of a link in condensation polymerisation?
A
- It determines what type of polymer is produced
aka polypeptides, polyamides (amide link) & polyesters (ester link)
16
Q
Why must a dicarboxylic acid and diamine be used to form a polyamide?
A
- We have to dicarboxylic acids and diamines as they have functional groups either side which allows for chains to be formed
17
Q
Why can’t a cabroxylic acid be used to form a condensation polymer?
A
- A condensation polymer must be formed from a DIcarboxylic acid
- because there must be functional groups on either side of the carboxylic acid to allow for chains to be formed
18
Q
Draw the Repeating unit of Kevlar and describe its uses
A
- Kevlar is a polyamide that is used in bulletproof vests, car tyres and sports equipment
- it is light weight but strong
- Kevlar -> benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene
(inset pic)
19
Q
For a Polyester chain formed of n = 20 of a Dicarboxylic acid and Diol, how many water molecules are produced
A
19
20
Q
Draw the Repeating unit of Nylon 6,6 and describe its uses
A
Nylon 6,6 is a polyamide that is used in ropes, carpets, clothing and parachute fabric
- Nylon 6,6 -> hexanedioic acid and 1,6-diaminohexane
21
Q
Draw the Repeating unit of Terylene (PET) and describe its uses
A
- Terylene is a polyester that is used in plastic drinks bottles, sheeting and clothes
- Terylene -> benzene-1,4-dicarboxylic acid and ethane-1,2-diol
(insert pic)
22
Q
How can Condensation Polymers be broken down?
A
- Hydrolysis (split using water)
- This produces the original monomers
- This is due to the fact that they have polarity caused by the C=O and C-N bonds that exist in the polymer chain
23
Q
Condensation Polymers vs Addition Polymers
A
- Condensation polymers are usually more rigid and stronger than their addition polymer counterparts
- Condensation polymers have polar bonds allowing them to have strong intermolecular forces - Hydrogen bonds, Vanderwaals & dipole-dipole
24
Q
Uses of Polymers and their degradability
A
Synthetic Polymers - made from monomer units and used to make plastic bottles, digital tech, non-stick coating on pans
- polyalkenes are great to use for foods like cups,bowls etc because they are unreactive
- some are biodegradable: condensation polymers
- some are not biodegradable: Addition Polymers
25
Why are Condensation Polymers Biodegradable
-Condensation polymers are polar and are hence susceptible to attach from nucleophiles
- They are biodegradable and broken down by hydrolysis slowly
26
Why are Polyalkenes non-biodegradable?
- They are saturated molecules
- normally non-polar
- hence unreactive
- means it cannot undergo reactions to break it down e.g hydrolysis with condensation polymers
- meaning they don’t degrade well in landfill
27
Means of Disposing Plastics
- Landfill
- most polymers are not biodegradable
- used for disposing plastics that…
• too difficult to recycle
• are too difficult to separate from other materials
• not enough plastic to extract to make it economically viable
- Incineration
- for non biodegradable plastics that can’t be recycled
- the energy generated from burning can be used to generate electricity
Recycling
- recycling means reducing dependency on crude oil for making plastics
- some plastics can be **re-moulded**
- some plastics can be **cracked** into monomers and used as **organic feedstock** for plastics
28
Risks of Landfill
- When waste decomposes in landfill it produces methane which is a greenhouse gase
- There is also a risk of **water contamination** from waste leaching
- Landfill is not very sustainable as large amounts of landfill is needed
- it becomes increasingly expensive to use it so our use of it must be reduced
29
How are Flue gas scrubbers used when disposing plastics?
- Flue gas **scrubbers** are used to neutralise acidic gases produced like HCl during **incineratuon**
- They work by firing a **base** at the flue gases. (e.g CaOH)
- This is Because burning plastics releases **toxic** fumes which need to be monitored
- particularly chlorine based plastics (e.g PVC) due to HCl
30
Pros and Cons of Recycling Plastic
-Disadvantages
- Plastics can be contaminated with other materials when recycled
- it is difficult to recycle plastics due to the wide variety of them
- it is difficult to re-make the of plastic from recycled material, poorer quality
- sorting and processing plastics to be recycled is expensive
- Advantages
- it is cheaper to recycle plastics than make them from scratch
- less CO2 produced recycling plastics than incinerating them
- recycling reduces reliance on landfill
- recycling preserves non-renewable raw materials such as crude oil
31
What are Amino Acids composed of?
- an amino group (-NH2)
- a carboxyl group (-COOH)
- R group
32
Why are amino acids amphoteric?
- They have both acidic and basic properties
33
What is the structure of an Amino Acid
- amino group (-NH2)
- carboxyl group (-COOH)
- R group (organic side chain)
- All amino acids (accept for Glycine) are **chiral molecules**, thus they **rotate plane polarised light**
34
Why are Amino acids considered to be amphoteric?
- They have both acidic and basic properties
35
What is a Zwitterion?
- A zwitterion is a molecule with **both** positive and negative ions
- Zwitterions only exist at the amino acids. **isoelectric point***
36
What is the isoelectric point of an amino acid?
- The isoelectric point is the pH at which the average overall charge is **zero**
- This is dependent on the ‘R’ group
37
What happens to a zwitterions at Low pH?
- If the pH is lower than the **isoelectric point** then COO- is likely to **accept** H*
- this will occur if put in a more acidic solution
38
What occurs when a zwitterion is in a solution = to the pH of the isoelectric point
- A zwitter ion is likely to be formed when at a pH at the isoelectric point
- Both the carboxyl and amino groups are ionised
39
What happens to a zwitterions at High pH?
- If the pH is higher than the **isoelectric point** then NH3+ is likely to **lose** an H+
- this will occur if put in a more alkaline solutuon
40
How can different amino acids be identified?
- Thin Layer Chromotography
- It allows us to separate and identify amino acids as they have different solubilities
41
What is the stationary phase used for TLC?
- typically **silica** or **alumina** mounted on a glass/metal plate
42
Steps required for Thin Layer Chromotography
- use a silicone if alumina mounted on a glass/metal plate
- a Pencil base line is drawing and drops of amino acid mixtures added
- Place the plate in a solvent - the base line must be above the solvent level
- leave until solvent has moved up to near the top of the plate
- Remove, mark the solvent front and allow to dry
- Use UV light to view the results and take readings of the mobile phase
(insert pic)
43
Why does Thin Layer Chromotography work with Amino acid mixtures?
- It works by the amino acids mixture spots dissolving in the solvent
- Some chemicals in the mixture may not dissolve as much and stick to the **stationary phase** quickly/are more attracted to the stationary phase.
- Leaving you with a clear chromatogram
44
How can the results of chromatograms be seen so that they can be analysed?
- Amino Acids are colourless compounds however they can be seen using:
• Fluorescent dye and UV light - the colourless spots will block any flow from the fluorescent dye
• Iodine/ninhydrin solution (leave chromatorgram in a sealed jar with a few iodine crystals, the iodine vapour sticks to the chemicals)
45
How can the Rf values from TLC be used to identify amino acids?
- the number of spots on the plate corresponds to how many amino acids make up the mixture
- the amino acids a can be identified by calculating the Rf values and **comparing** these to a library of known Rf values
where Rf = distance travelled by spot/ distance travelled by solvent
46
What is a Protein?
- Polymers that are made up of amino acid monomer units
- they are a type of condensation polymer
47
What is a peptide link?
- amino acids joined together form a link to form a polypeptide
- the link is referred to as the peptide link
48
How can Proteins be broken down? Why may we want to do this?
- The protein can be broken down into amino acids via hydrolysis
- It requires the “severe” conditions: 6moldm^-3 of HCl, reflux for 24hours
- Can be used to determine what amino acids have been used by breaking the peptide link to find the individual monomers
49
Due to protein existing as complex molecules, how many levels of structure are there?
Primary, Secondary, Tertiary, Quaternary
= 4
50
What is the Primary structure of a protein?
- A primary protein structure shows the individual sequence of amino acids that make up the protein
- aka the protein/polypeptide chain
(each black line represents a peptide link)
51
What is the Secondary structure of a protein?
- How the polypeptide chains interact with each other
- Hydrogen bonds exist between the peptide links in the polymer chain
- these pull straight chains into **coiled** or **pleated** structures
- Secondary structures come in two forms:
- α helix chain
- β pleated sheet
(insert image)
52
What is the Tertiary structure of a Protein
- The protein chain is long and often it coils itself up giving a unique shape for that protein
- additional bonds hold the long coiled chain together
53
How are proteins’ specific shapes held in place?
- Proteins have **specific shapes** which are held in place by **hydrogen bonds** and **disulfide bonds**
(inset pic)
54
What causes the 3D shapes attained by proteins and why are they important?
- Intermolecular forces create the twisting features of secondary and tertiary structures
- this gives proteins **specifc 3D shapes** that **determines** it’s basic functions e.g.enzymes
55
What are the 2 types of bonds that hold a protein shape?
- Disulphide bonds
e.g. cysteine has a **thiol group** (-SH), they can lose the H atom and form a sulfide bond (S-S)
- Hydrogen bonds
- exists between highly electronegative relents such as O and N with H
- amino acids have -NH2 and -OH
- if any of these bonds are broken it will alter the tertiary or secondary structure of the protein
56
What conditions affect the type of bonding between polypeptide chains and thus the secondary structure of proteins?
- **Temperaure** and **pH** change the shape of proteins by affecting **hydrogen bonding** and the formation of **disulphide bonds**
57
What are Enzymes and what are Substrates?
- Enzymes are proteins and are biological catalysts that speed up chemical reactions
- all enzymes are **proteins** (though some have non protein elements)
- **Substrates** are molecules that enzymes **interact** with to speed up reactions
58
How are Enzymes specialised to act as a catalyst?
- Enzymes have a 3D active site which is part of the **tertiary protein structure**
- This is where the chemical reactions occur and **substrates** can interact with the enzyme
- Enzymes only work with specific substrates as the active site has a **fixed** shape
59
How do Enzymes work?
- Enzymes work by receiving the correct shaped substrate into the active site
- the shape must match to be catalysed
(insert pic)
60
Why are Enzymes Stereospecific?
- enzymes have **chiral centres** as they are made up of amino acids
- meaning only **one enatiomer** in the substrate will fit into the active site
- thus active sites are **stereospecific**
61
How can the rate of reaction of an enzyme-catalysed reaction be slowed down?
- The rate of reaction can be slowed down by using inhibitors to block the active site from the **substrate**
- An inhibitor is a substance that has a **similar shape** to the substrate that fits into the active site of an enzyme
- An inhibitor blocks the active site from a substrate, the higher the **concentration of inhibitor** the **more active sites** blocked and thus the rate of reaction decreases
- how strongly an inhibitor binds to an active site also effects the rate, e.g. a poorly binding inhibitor will not reduce rate as much
62
How do scientists develop new drugs like antibiotics and why?
- Trial and Error method
- enzyme active sites are stereospecfic so it can be difficult to find drugs that fit into the active site
- if the drug is chiral only one enantiomer will work
- thus scientists try different inhibitors to see which work, and refine them
63
How can drug development be sped up?
- Through the use of computer modelling to design new drugs to act as inhibitors
- the computer models test how drugs will respond to enzymes without making the drug
- quicker and cheaper process
64
What is DNA?
- a polymer that is made up of monomers called nucleotides
- A nucleotide is made up of 3 components:
- A phosphate
- A sugar
- A base
(inset pic)
65
How are Polynucleotide chains formed?
- Polynuecleotide chains are formed by joining nucleotides together
- Phosphate on one nucleotide is **covalently bonded** to a sugar on another
- this creates the **sugar-phosphate backbone**
66
How is the sugar-phosphate backbone in DNA formed?
- via condensation polymerisation using nucleotides as monomers
- A phosphodiester bond is formed and water is eliminated
- the OH group on the phosphate and sugar group react further to extend the polymer chain
67
What shape is DNA? What is it composed of?
- Double Helix
- formed from 2 polynucleotide strands twisted
- Held together by hydrogen bonds between them
68
What are the complementary base strands?
- Adenine with Thymine (A-T)
- Cytosine with Guanine (C-G)
69
How is the sugar-phosphate backbone in DNA formed
- via condensation polymerisation using nucleotides as monomers
- A phosphodiester bond is formed and water is eliminated
- OH groups on the phosphate and sugar group react further to extend to polymer chain
70
What holds the polynucleotide strands together?
- Hydrogen bonds between the bases
71
What are the complimentary base pairs?
- Adenine bonds with Thymine (A-T)
- Cytosine bonds with Guanung (C-G)
- Bases are paired up in specific ways and are joined together via hydrogen bonding
72
What are to conditions for hydrogen bonding to occur between Base Pairs?
- Hydrogen bonds can only form when a delta positive Hydrogen interacts with an electronegative element with a lone pair of electrons such as O of N
- and the correct distance apart
73
How many hydrogen bonds can each base pair make between one another in a double helix
- A and T form hydrogen bonds as there are **2 atoms** to form a hydrogen bond
- G and C form hydrogen bonds as there are **3 atoms** between G and C
74
Why are there only two base pairs for which hydrogen bonding can occur?
- No other based pairings (other than A-T and G-C) can happen as the partial charged on the atoms would be too close and repel one another OR
not get close enough to form a hydrogen bond
75
What is Cis-platin? and how is it used?
- An anti-cancer drug
- Square planar complex with a platinum metal ion
- formed with 2 ammonia ligands and 2 chloride ion ligands
- Cancer is made up of cells that multiply in an uncontrollable fashion to form a **tumour**, via DNA replication
- Cis-platin **binds** to **DNA** in cancer cells
- As the cell is attached to the DNA it prevents the cell **reproducing** through cell division.
- The cell dies unable to repair itself
- important that is structure as “cis” because trans-platin has the Cl atoms opposite each other and has a different effect
76
What are the features of the Cisplatin that allow for it to work as an anti-cancer drug?
- The chloride ions in the complex are easy to displace and can detach from the complex
- the platinum can then bind to the **nitrogen** atoms on the **guanine** base within the **DNA** of the cancer cells
- The cis-platin bonds to the DNA creating a distortion to the DNA strand, preventing it from unwinding and being copied
77
Problem with Cis-platin as an anti-cancer drug
- Cis-platin is very effective against cancer but it is also effects healthy cells from reproducing
- e.g it can suppress the immune system by effective blood cells, hair cell damage, kidney damage, increase risk of infection etc
78
How can the side effects of cisplatin be reduced?
- giving lower doses
- targeted delivery of the drug
- both reducing the attack on healthy cells
79
How can haloalkane be formed from an alkane?
- Free radical substitution
reagents:
- Halogen (X₂)
- UV light
80
How can an Amine be made using a Halogenoalkane?
WAY 1:
- Nucleophilic Substitution
reagents: NH₃, heat
WAY 2:
- Nucleophilic Substitution + Reduction
forming nitrile:
reagents: KCN (ethanolic), heat, reflux
reducing nitrile:
H₂, Ni, 200 °C
or LiAlH₄
81
How can an Amide be formed from an amine?
- nucleophilic addition elimination
- addition of an acyl chloride/ acid anhydride
82
How can alkene be formed from a haloalkane?
- Elimination
- KOH/NaOH (ethanolic)
- reflux/hot
83
How can an alkene be formed from an alcohol?
- nucleophilic substitution
- Conc H₂SO₄
- 180 °C
84
How can a haloalkane be formed from an alkene
- electrophilic addition
- addition of HX where X is a halogen
85
How can an alcohol be formed **directly** from an alkene?
- Hydration
- Conc H₃PO₄
- High Temperature
- High Pressure
86
How can an Alkene be formed formed when using an alkyl hydrogensulphate?
- hydrate alkyl hydrogensulphate to form alcohol
conditons: dilue, warm
- add concentrated sulphuric acid at 180°C to form alkene
87
How can an Alkane be formed from an Alkene?
- Reduction reaction, hydrogenation
- reagents & conditions: H₂, Ni at 200 °C
88
How can an alcohol be formed from a Haloalkane?
- Nucleophilic substitution
- conditions: NaOH(aq), warm
89
How can an Amine be formed from a nitrile?
- reduction
- H₂, Ni, 200 °C
or LiAlH₄
90
Reaction pathway for Alcohol to Esther
- Carboxylic Acid, conc H₂SO₄
or acyl chloride, acid anhydride
- Esterification
91
Carboxylic acid to Ester
- Alcohol, conc H₂SO₄
- Esterification
92
Alcohol to Ketone, Carboxylic Acid & Aldehyde
Ketone & Carboxylic Acid
Kr₂Cr₂O₇, H₂SO₄, reflux
Oxidation Reaction
Aldehyde
Kr₂Cr₂O₇, H₂SO₄, heated and distilled
Oxidation reaction
93
Ketone and Aldehyde to Alcohol
- NaBH₄(aq)
- Reduction reaction
94
Ketone or Aldehyde to 2-Hydroxynitrile
- Nucleophilic **Addition**
- additIon of HCN
95
Aldehyde to Carboxylic Acid
Further oxidation reaction
- addition of Kr₂Cr₂O₇ or H₂SO₄ under reflux/heat
or
- addition of Tollen's reagent Ag[NH₃]₂
- addition of Fehling's solution
Kr₂Cr₂O₇ is the stronger oxidisng agent and is used to fully oxidise rather than for simple tests like the other two are
96
How can aliphatic pathways and aromatic pathways be differentiated?
- Whether there is a change to the benzene ring or not
97
Benzene to Cyclohexane?
- Hydrogenation
- H₂, Ni (catalyst), 100 °C
98
Benzene to Benzoyl chloride
- Friedel crafts acylation
- mechanism: electrophilic substitution
- RCOCl/ acid anhydride, AlCl₃
- Reflux
- warm, aqueous
99
benzene to nitrobenzene
- Nitration
- conc HNO₃, conc H₂SO₄
- below 55 °C
(if TNT then x3)
100
Nitrobenzene to phenylamine + reactions involved
- Reduction reaction
- reagents: Sn, Conc HCl, NaOH(aq)
(simplified)
1. Sn + HCl -> NH₃⁺
2. NaOH -> NH₂
101
phenylamine to N-phenylamide
- reaction: Acylation, Condensation reaction
-mech: nucleophilic addition elimination
- reagents & conditions: acyl chloride/acid anhydride, 25°C
