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41 Cards in this Set
- Front
- Back
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Why do we accept benzene's delocalised structure?
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X-ray studies --> C-C lengths were all the same (between C-C and C=C)
ΔHhydrogenation is -208, not -360 kJmol^-1 Benzene does not decolorise with bromine water (pi electron density insufficient in benzene) |
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Why is bromine resistant to bromination compared with alkenes?
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Relatively low density of delocalised electrons in benzene compared with alkenes (C=C double bond)
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Phenol + aqueous alkalis/sodium -->
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Salts
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Phenol + Bromine
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2,4,6-tribromophenol
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Whey is phenol easier to brominate compared with benzene?
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The -OH donates an electron pair to the benzen ring from an oxygen p orbital in the phenol
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What are phenols used for?
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Plastics, antiseptics, disinfectants and resins for paints
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What is the reagent for reducing carbonyl compounds, what's formed?
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NaBH4, alcohols
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What is 2,4-dinitrophenylhydrazine used for?
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To detect the presence of carbonyl groups
Identify a carbonyl compound from the MELTING point of the derivative |
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What is Tollens' reagent?
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Ammoniacal silver nitrate
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What is Tollens' reagent used for?
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Detect the presence of an aldehyde group
Distinguish between aldehydes and ketones. Aldehydes are oxidised to carboxylic acids with the reduction of silver ions to silver |
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Hydrolysis of esters in hot aqueous acid forms...
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Carboxylic acid + alcohol
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Hydrolysis of esters in hot aqueous alkali forms...
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Carboxylate salts and alcohols
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What is a triglyceride?
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A triester of glycerol (propane-1,2,3-triol) and fatty acids
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What happens when you have a lot of trans fatty acids?
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Increase in 'bad' cholesterol (LDLs) --> risk of CHD and Strokes
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What are esters and fatty acids used for?
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Biodiesel
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Explain the basicity of amines
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A proton is accepted by the nitrogen lone pair
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Amine + acid -->
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Salt
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How do you prepare an aliphatic amine?
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Substitution of halogenoalkanes with excess ethanolic ammonia
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HOw do you prepare aromatic amines?
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By reduction of nitroarenes using tin and concentrated hydrochloric acid
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How do you produce an azo dye?
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Reaction of an aromatic amine with nitrous acid (<10*C) with formation of a diazonium ion, followed by coupling with a phenol under alkaline conditions
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What is the general formula for an alpha-amino acid?
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RCH(NH2)COOH
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Amino acids exist as zwitterions at a pH value called the __________ _____
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Isoelectric point
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What is an optical isomer?
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A non-superimposable mirror image about an organic chiral centre: four different groups attached to a carbon atom
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Optical and E/Z isomerism are different types of _______________
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stereoisomerism (types of isomers are structural, stereo and optical)
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Condensation polymerisation forms...
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Polyesters (e.g. Terylene) and polyamines (e.g. nylon-6,6)
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What are polyesters and polyamides used for?
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Fibres in clothing
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What is the role of chemists to minimise environmental waste?
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To develop degradable polymers (such as poly(lactic acid))
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Which polymer may be photodegradable and why?
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Condensation polymers, the C=O bond absorbs radiation
Condensation polymers can also be hydrolysed at the ester or amide group |
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A single optical isomer is often required in the...
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Synthesis of pharmaceuticals
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Synthesis of a pharmaceutical that is a single optical isomer...
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Increases costs due to difficulty in separation
Reduces possible side effects and IMPROVES PHRMACOLOGICAL ACTIVITY |
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How do you synthesise a pharmaceutical with a single optical isomer?
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Using enzymes or bacteria
Using chemical chiral synthesis/chiral catalysts Using natural chiral molecules such as L-amino acids or sugars as STARTING MATERIALS |
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What is chromatography?
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An analytical technique that separates components in a mixture between a mobile phase and a stationary phase
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What state can the mobile phase be? (Think)
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Liquid/Gas
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How dos a solid stationary phase separate?
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By adsorption
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How does a liquid stationary phase separate?
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By relative solubility
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What is the 'retention time'?
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In GC, it is the time for a component to pass from the column inlet to the detector
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How is the Rf value calculated?
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Distance moved by component/Distance moved by solvent front
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What are the limitations of GC?
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Similar compounds often have similar retention times
Unknown compounds have no reference retention times for comparison |
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What is the use of GC-MS?
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Analysis, e.g. in forensics, environmental analysis, airport security and space probes
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What does NMR spectroscopy involve?
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Interaction of materials with the low-energy radiowave region of the electromagnetic spectrum
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What is TMS?
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Tetramethylsilane, standard for chemical shift measurements
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