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Flashcards by nicola.bowen, updated more than 1 year ago
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Created by nicola.bowen
almost 10 years ago
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| Question | Answer |
| Define an electrophile | an atom that accepts a pair of electrons |
| What are the reagents and conditions required for nitration of benzene? | concentrated HNO3 and H2SO4 catalyst, 50 degrees temperature |
| Why is nitration of benzene carried out at 50 degrees? | A higher temperature may lead to more than one nitro group being substituted |
| Name a suitable halogen carrier for halogenation of benzene | Al Br3 or Fe Cl3 |
| Write two equations to show H2SO4 as a catalyst in nitration of benzene | HNO3+H2SO4 > NO2+ + HSO4- + H2O |
| What kind of reaction is nitration of benzene? | Electrophilic Substitution |
| Write two equations to show AlBr3 as a catalyst in halogenation of benzene | AlBr3+Br2 > AlBr4- + Br+ AlBr4-+H >AlBr3 + HBr |
| Why does bromine readily react with cyclohexene and not benzene? | In cyclohexene the electrons are localised across the double bond and have a high enough density to induce a dipole in bromine, whereas in benzene the electrons are delocalised and cannot induce a dipole, hence the need for a halogen carrier. |
| When bromine is added to cyclohexene what would you see? | Decolourisation of bromine water |
| What is the organic product called when sodium hydroxide is added to phenol? | Sodium phenoxide |
| What organic product is formed from the reaction of phenol with bromine? | 2,4,6 - tribromophenol |
| Why does phenol react readily with bromine? | The lone pair on the oxygen atom is drawn into the benzene ring increasing electron density which is capable of inducing a dipole in bromine. |
| Name some uses of phenol | making dyes, making pharmaceuticals, detergents |
| What is the reducing agent used to reduce ketones and aldehydes to alcohol? | NaBH4 |
| What symbol is used in equations to represent the reducing agent? | (H) |
| What kind of reaction is the reduction of ketones and aldehydes? | Nucleophilic addition |
| Define a nucleophile | An atom that donates a pair of electrons to form a new covalent bond |
| What is the systematic name for Bradys reagent? | 2,4-dinitrophenylhydrazine |
| If an orange precipitate forms upon addition of Bradys reaction what must be present in the solution? | A ketone or aldehyde |
| How can you distinguish between a ketone and aldehyde? | Add Tollen's reagent and if a silver mirror forms it is an aldehyde |
| How can you make Tollens reagent? | Add silver nitrate to sodium hydroxide, then add ammonia until the precipitate just dissolves |
| Is Tollens a reducing or oxidising agent? | Oxidising |
| How can you identify a carbonyl compound? | Purify the product through recrystallisation and measure the melting point which can be compared to a table of known values |
| Define hydrolysis | A reaction with water or hydroxide ions that breaks a chemical compound into two chemical compounds |
| What is the advantage of using acid anhydrides and alcohol to form an ester instead of an alcohol and carboxylic acid? | better yield and no need for a catalyst |
| What are the products formed in acid hydrolysis of an ester | Alcohol and carboxylic acid |
| What is the catalyst in acid hydrolysis of an ester | dilute HCl |
| What are the products formed during alkaline hydrolysis of an ester | a salt and alcohol |
| What are the meanings of each symbol in the short hand notation for a fatty acid X:Y (N) | X = number of carbons Y = number of double bonds (C=C) N = position of double bonds |
| What is the structure of glycerol? | CH2(OH)CH(OH)CH2(OH) |
| Which stereoisomer of fatty acids can pack closer together? | Trans as the structure is more linear |
| What are the functions of HDLs? | High density lipoproteins which transport cholesterol out of the blood and eventually out of the body |
| What are LDLs? | These are low density lipo-proteins which transfer lipids onto artery walls and build up fatty deposits |
| How do you make biodiesel? | Transesterification - react a triglyceride with methanol in the presence of NaOH catalyst |
| What is a primary amine? | An amine with only one carbon chain attached to the nitrogen atom |
| Why are amines defined as weak bases? | Each has a lone pair on the nitrogen atom which can accept a proton |
| How can aliphatic amine be prepared? | react halogenalkanes with an excess of ammonia using ethanol as the solvent |
| What kind of reaction is the preparation of primary amines? | Nucleophilic substitution |
| Why is excess ammonia used in the preparation of primary amines? | To minimise the chance of further substitution occurring |
| How can aromatic amines be prepared? | Use tin catalyst and concentrated HCl , heated under reflux followed by neutralisation of excess acid |
| What products are formed from the reaction of nitrobenzene with HCl in presence of tin? | Phenylamine and water |
| What is diazotisation? | Forming a diazonium ion when a mixture of phenylamine and nitrous acid is kept below 10 degrees |
| How is nitrous acid produced during preparation of the diazonium ion? | React together sodium nitrite and HCl: NaNO2+HCl>HNO2+NaCl |
| What is a coupling reaction? | When the diazonium ion ion is reacted with a phenol under ALKALINE conditions...the two benzene rings are linked together through the azo group -N=N-, usually on the carbon at position 4 of the phenol if it is free |
| Define a peptide | A compound made of amino acids linked by peptide bonds |
| Define an alpha amino acid | An amino acid that has both a basic group and acidic group attached to the carbon |
| What is the general formula of an amino acid | RCH(NH2)COOH |
| define a zwitterion | A dipolar form of an amino acid that is formed from the donation of a hydrogen ion from the carboxyl group to the amino group...no overall charge as both charges are present |
| Define isoelectric point | the pH value at which the amino acid exists as a zwitterion |
| What is amphoteric | can react with both acids and bases |
| What happens to an amino acid when the pH is more alkaline than the isoelectric point? | It becomes negatively charged as the amino group loses a proton into solution |
| What happens if the pH is more acidic than the isoelectric point? | The amino acid becomes positively charged as the carboxyl group accepts a proton from the solution |
| Define a condensation reaction | Two small molecules react together to form a larger molecule with the elimination of water |
| Which products are formed from the acidic hydrolysis of a dipeptide? | Two positively charged amino acids due to the presence of H+ ions in the acid |
| What are the reagents and conditions for acidic hydrolysis of polypeptides? | 6MHCl under reflux for 24 hours, water |
| What products are formed from alkaline hydrolysis of a polypeptide? | Sodium salts |
| What conditions and reagents are required for alkaline hydrolysis of polypeptides? | 100 degrees and NaOH |
| Define a chiral carbon | A carbon which has four different groups attached |
| Define optical isomerism | Stereoisomers that are non superimposable mirror images of each other |
| What is the main difference between the different enantiomers? | Rotate plane polarised light in different directions |
| What is a mixture containing both enantiomers called? | A racemic mixture |
| What kind of monomers does condensation polymerisation require? | Monomers with two different functional groups |
| What is the link called in polyesters? | Ester linkage |
| Which two kind of monomers can be used to form polyesters? | A monomer with an alcohol group and carboxylic group or a dioic acid and a di-ol |
| How many waters are produced from n monomers during polymerisation? | 2n-1 |
| Define a biodegradable polymer | A polymer that breaks down completely into carbon dioxide and water |
| Define a degradable polymer | A polymer that breaks down into smaller fragments when exposed to light, heat or moisture |
| What are the products from acidic hydrolysis of a polyamide | the dicarboxylic acid and ammonium salt of diamine |
| What are the products from alkaline hydrolysis of polyamides? | The sodium salt of dicarboxylic acid and the diamine |
| What are photodegradable polymers? | Synthetic polymers which become weak when exposed to sunlight for a long period of time |
| Define pharmacological activity | the beneficial or adverse effects of a drug on living matter |
| name some disadvantages of using a racemic mixture in a drug | Harmful side effects could be caused by the unwanted optical isomer, double the dose is required and increased cost |
| How can you separate a racemic mixture? | use of enzymes, electrophoresis or chromatography |
| How can you prepare a single isomer? | Use enzyme as biological catalysts, chiral pool synthesis and use of transition metal complexes. |
| Define mobile phase | The phase that moves in chromatography |
| Define stationary phase | The phase that does not move in chomatography |
| How does a solid stationary phase separate components? | Adsorption |
| How does a liquid stationary phase separate components? | By relative solubility |
| What is the stationary phase in tlc? | Silica gel |
| define a chromatogram | A visible record showing the result of separation of the components of a mixture by chromatography |
| how do you calculate the Rf value? | (distance moved by component)/(distance moved by solvent) |
| What are some limitations of tlc? | many compounds have similar Rf values and some have unknown values. Difficult to find a suitable solvent |
| Describe how gas chromatography works | Mixture is vaporised in the chromatograph, the mobile carrier flushes the mixture through the column and the components slow down as they interact with the stationary phase resulting in different retention times |
| define retention time | the time for a component to pass from the column inlet to the detector |
| Give some uses for GC-MS | Forensic science, environmental analysis, airport security and space probes |
| Define chemical shift | a scale that compares the frequency of an NMR absorption with the frequency of the reference peak |
| What is TMS? | The reference peak...tetramethylsilane |
| Why is TMS used? | It has twelve equivalent protons and so leads to one single sharp peak |
| what kind of solvents are used for NMR analysis? | Deuterated solvents like CDCl3 |
| What can a carbon NMR spectrum tell us? | the number of environments and the type of carbon environment |
| What can a proton NMR tell us? | the number of environment, relative proton numbers in that environment, type of environment and number of protons attached to adjacent carbon |
| how many adjacent protons are next to the protons causing a triplet? | 2 non equivalent protons |
| how can you identify a OH or NH peak? | Add D2O and the peak produced due to these protons will disappear |
| What is the equation for the addition of D2O to ethanol? | CH3CH2OH+D2O > CH3CH2OD + HOD |
| Give some uses of NMR | MRI scans, body scanning - sports injuries |
| What are some advantages of using NMR in medicine? | Non - invasive, harmless, low energy radiation |
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