Transcript Slide 1
Describe the structural formulae and reactions of compounds containing selected functional groups 4 credits Selected organic functional groups are limited to: • Haloalkane • Alcohol • Alkene • Alkyne • Ester • Carboxylic acid Compounds are limited to: Those containing no more than 8 carbons. Larger organic molecules may be used in Qs linking structure & reactivity. Naming compounds Structural and geometric isomers Knowledge of primary, secondary & tertiary alcohols & haloalkanes polymerisation Organic Chemistry Reactions of alkenes H2/Pt Br2 Distinguishing tests Cl2 MnO4H2O/H+ & HCl identify major & minor products Acid reactions of carboxylic acid Halogenation of alkanes Elimination of water from alcohol Oxidation of primary alcohols to carboxylic acid Formation & hydrolysis of esters e.g. triglycerides Fats, oils and soaps •Triglyceride is a fat that contains 3 ester links •Made from 3, long-chain carboxylic acids + glycerol (triol) •In the esterfication reaction, 3H20 is formed (OH from acid + H from glycerol) Beware; they can change the orientation Divide between C and O, add Hs to form triol and OHs to form acid Fats, oils and soaps Like all esters, triglycerides undergo hydrolysis. This reaction can be catalysed by either acid or base. 1.With acid An acid catalyst is used (not conc. acid) to form glycerol (triol) and carboxylic acid again: 2.With alkali (OH-) If NaOH is used, it reacts with the carboxylic acid to form a sodium salt and glycerol. The sodium salt in this case is called ‘soap’ and the reaction is called ‘saponification’ Acid conditions: glycerol and palmitic acid formed. Alkali conditions: glycerol and the sodium salt of palmitic acid formed Notice there are 3 diff. acids In basic conditions: glycerol would still form but instead of the acid a sodium salt would form. Na Polymerisation •A polymer is a large molecule made of small molecules called monomers •In addition polymerisation, nothing else is made •All monomers are alkenes •Could be asked to draw monomers from polymers or vice versa Isolate 2 OH carbons to form the basis CH=CH 2 of the alkene monomer Break the double bond, attach to next monomer Isolate 2 carbons, straighten them and put the double bond in Naming compounds Learn functional groups and endings! Group Alkane Alkene Alkyne Alcohol Haloalkane Carboxylic acid Ester Structure C-C C=C C=C -OH e.g. –Cl OH C=O -C=O O Name ending -ane -ene -yne -anol e.g Chloro-ane -anoic acid -thyl-anoate Crocodiles! What is eaten first is named first! 1-chloropropane methylpropanoate Numbering begins at ene end -anoic grp is always on carbon 1 Structural isomers Same number of atoms in a different arrangement Geometric isomers • Different arrangements of atoms in space • Cis (same side) & trans (across) • Due to double bond being unable to rotate • Can have different properties e.g. polarity & boiling point Don’t need to give number placing for methyl and ene. They can be nowhere else! methylpropene cyclobutane But-1-ene Cannot form cis & trans because the groups on each C are not different Base the drawing around the double bond to examine the groups But-2-ene Can form cis & trans because the groups on each C are different and the double bond doesn’t allow rotation Remember this! It’s the stock answer for explaining geometric isomers Reactions of alkenes All types of addition reactions Reaction type Reagent Hydrogenation Hydrogen Watch out for Markovnikov’s! Asymmetrical Conditions Product alkene = 2 products Hydration Water Pt/H2 or Ni/H2 H+/H20 Halogenation Halogen Br2 or Cl2 Haloalkane Halogenation Hydrogen HCl or Haloalkane halide HBr Potassium H+/MnO4- Diol Watch out for permanganate Oxidation Markovnikov’s! Asymmetrical alkene = 2 products Alkane Alcohol Primary, secondary & tertiary • Classifications in alcohols and haloalkanes • Look at the Carbon the alcohol/halogen is attached to. Is this attached to 1, 2 or 3 carbons? • Form straight line (!), T-shape or cross primary secondary primary tertiary Reactions of alcohols • Elimination of water (dehydration): Conc. H2SO4 alcohol Alkene + water • Oxidation of 1° alcohol: H+/Cr2O72- 1° alcohol (aldehyde) Carboxylic acid Dichromate turns from orange to green Can use H+/MnO4- as oxidising agent instead. Purple to colourless • Esterfication: Conc. H2SO4 alcohol + Carboxylic acid ester This is a dehydration reaction (elimination) Alcohol + acid… Oxidation of a primary alcohol… Potassium permanganate will turn from purple to colourless Reactions of carboxylic acids • Normal acid reaction e.g. fizzing with metal H2 & fizzing with carbonates CO2 & litmus turning red • Form metal salts involving the organic acid e.g. sodium methanoate • Form esters when reacted with alcohols Distinguishing tests Group H+/Cr2O72- Sodium Smell carbonate sol. Warm H+/MnO4- Alcohol 1° turns from orange to green Forms 1 layer 1° turns Stays from orange purple to colourless Haloalkane Stays orange Forms 2 layer Stays purple Stays orange Stays orange pungent Stays Forms 1 layer that purple fizzes Stays orange Ester Stays orange Forms 2 layers Stays purple Stays orange Alkane Stays orange Forms 2 layers Stays purple Slowly decolour w/ uV Alkene Stays orange Forms 2 layers Carbox. Acid Damp litmus Turns red fruity strong Bromine water Purple to Quickly colourless decolour Acidified potassium dichromate (H+/Cr2O72-) Propan-1-ol will turn acidified potassium dichromate from orange to green. Propanoic acid will remain orange. There are other possible answers, see how many you can come up with! hexane Decolourises bromine slowly with UV light Saturated so undergoes a substitution reaction Forms 1-bromohexane hex-1-ene Decolourises bromine quickly unsaturated so undergoes an addition reaction Forms 1,2-dibromohexane CH3CH2CH2CH2CH2CH3 + Br2 CH2CHCH2CH2CH2CH3 + Br2 CH2BrCH2CH2CH2CH2CH3 + HBr CH2BrCBrCH2CH2CH2CH3 + HBr So B must be a primary alcohol and reagent D must be an oxidant Propan-2-ol End product = ester. Reagent = alcohol. So C To form a sodium saltmust of be… an ester… NaOH Adding water to an asymmetric alkene…but which product goes where? Propan-1-ol H+/Cr2O72- Propanoic acid