Organic chemistry Topic 10

Organic chemistry Chemistry of carbon compounds Carbon bonds four times

Organic structures [369] Formulas Structures Empirical Molecular Full Condensed In between

Shape of carbon compounds [369] Alkane - tetrahedral shape Alkene – trigonal planar Alkyne - linear Lines – in plane of paper Dash – behind plane of paper wedge – out of plane of paper

Organic nomenclature [370-374] 1) identify longest chain of carbon atoms 2) identify any functional groups 3) identify side chains Listed in alphabetical order Use of prefixes di, tri, tetra

Organic nomenclature [370-374] Number of carbons determine “stem” name See table page 370

Organic nomenclature [370-374] Functional groups are the “suffix” of the name See table page 371

Organic nomenclature [370-374] Side chains are the “prefix” of the name See table page 373

Exercises 1-4 pages 374-375

Structural Isomers [375-378] Compounds with same formula but different structure

Structural Isomers [375-378] Need to know structures and names of all isomers up to C6

Structural Isomers [375-378] Another type of structural isomer is positional isomer

homologous series [366-368] Successive compounds that differ by the addition of a CH2 (methylene) group CH4, C2H6, C3H8, …CnH2n+2 Similar chemical properties Physical properties vary in a regular manner Specifically melting point and boiling point

homologous series: trends in boiling points [366-368] Gradual increase in boiling point, melting point, volatility with increasing carbons Van der Waals forces Higher molar mass = stronger forces Increase slows down as the number of carbons increases, less percent increase in mass

homologous series: trends in boiling points [366-368]

1, 2, and 3 carbons [378-379]

1, 2, and 3 alcohols, etc. Applies to other functional groups Halogenalkanes, amines

IMF in organic compounds [380-381] Alkanes, enes, ynes – van der Waals Ester – dipole Aldehyde – dipole Ketone – dipole Amine – hydrogen bonding Alcohol – hydrogen bonding Carboxylic acid – hydrogen bonding Amide – hydrogen bonding

IMF in organic compounds [380-381] Polarity ranking of functional groups Amide>acid>alcohol>ketone~aldehyde> amine>ester>ether>alkane Stronger IMF lead to higher boiling points and higher water solubility As the carbon chain gets longer, water solubility decreases

IMF in organic compounds [380-381] Exercises 5-8 page 382

Reactions of alkanes [382- 385] Alkanes have strong bonds and are non polar, so low reactivity The only reactions are: Combustion (every hydrocarbon) Substitution with chlorine and bromine

complete and incomplete combustion Excess oxygen CH + O2 → CO2 + H2O Incomplete combustion Insufficient oxygen CH + O2 → CO + H2O

Balancing combustion reactions Complete combustion of butane Incomplete combustion of pentane Complete combustion of ethanol Exercise 9 page 385

Reactions of Alkanes [382- 385] Alkanes can reaction with halogens in the presence of UV light to form hydrogen chloride and a substituted alkane CH4 + Cl2 → CH3Cl + HCl This happens via a mechanism involving a free radical

Reactions of Alkanes [382- 385] A free radical is produced via homolytic fission AB → A + B each atoms remains with one lone electron highly reactive free radical

Reactions of Alkanes [382- 385] Initiation Cl2 + UV light → 2Cl Propagation Cl + CH4 → HCl + CH3 CH3 + Cl-Cl → CH3Cl + Cl Termination Cl + Cl → Cl2 or Cl + CH3 → CH3Cl or CH3 + CH3 → C2H6

Reactions of Alkenes [385-389] Hydrocarbons with double or triple bonds are called unsaturated, all single bonds are called saturated because they are saturated with hydrogen Alkenes can undergo addition and polymerization reactions

Addition reactions of alkenes [385-387] Hydrogen, water, halogens, and hydrogen halides can be added across a double bond

Uses of addition reactions [385-387] Bromination http://www.youtube.com/watch?v=PE1CDR1S5pk If bromine is added to an alkene, the brown bromine turns colorless as it reacts Hydration Industrial production of ethanol Hydrogenation Industrial production of saturated fats

Polymerization of alkenes [387-389] Important in manufacture of plastics Polyethene polymer Polychloroethene polymer (PVC) Polypropene polymer

Reactions of Alkenes Exercises 11-12 page 389

Reaction of alcohols [390-392] Oxidation 1 alcohol oxidized to aldehyde, then carboxylic acid 2 alcohol oxidized to ketone 3 alcohol cannot be oxidized

Reaction of alcohols [390-392]

distillation

reflux

Reaction of alcohols [390-392]

Exercises 13 and 14 page 392 Reaction of alcohols

Reactions of halogen alkanes [393-396] Carbon connected to halogen is + Susceptible to nucleophilic attack Nucleophile reactant that attack at center of positive charge by donating electron pair Good nucleophiles – OH-, NH3, CN-

Reactions of halogen alkanes [393-396] 1 halogen alkane undergo SN2 mechanism 2 halogen alkane undergo either SN1 or SN2 3 halogen alkane undergo SN1 mechanism SN1 faster than SN2 Rate of hydrolysis 3 > 2 > 1

Reactions of halogen alkanes [393-396] 1 halogen alkane + dilute base

Reactions of halogen alkanes Exercises 15 and 16 page 396

Reactions of halogen alkanes [393-396] 3 halogen alkane + dilute base

Reaction pathways But-2-ene  butanone

1-bromopentane  pentanoic acid Reaction pathways 1-bromopentane  pentanoic acid