Andrew's git - notes.git/blob - chem/organic-2.md

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   2geometry: a4paper, margin=2cm 
   3header-includes:
   4- \usepackage{mhchem}
   5- \usepackage{chemfig}
   6- \usepackage{tabularx}
   7- \usepackage{gensymb}
   8---
   9
  10# Organic Chemistry
  11
  12Large number of compounds due to:
  13
  14- 4 valence pairs
  15- single / double / triple bonds
  16- cyclic (ring) structures
  17
  18## Properties of hydrocarbons
  19
  20- *Saturated* - all C-C bonds are single
  21- Insoluble in water
  22- Almost non-polar (similar electronegativities)
  23- Only dispersion forces (valence e-)
  24- Dispersion forces increase with length
  25- Branched molecules have lower density
  26
  27## Linear (aliphatic)
  28
  29Alkanes: \ce{C_{$n$} H_{$2n+2$}}  
  30Alkenes: \ce{C_{$n$} H_{$2n$}}  
  31Alkynes: \ce{C_{$n$} H_{$2n-2$}}
  32
  33## Naming hydrocarbons
  34
  35- Branches end with _-yl_
  36- Indicate number of branches with di-, tri- etc.
  37- Longest unbranched carbon chain includes function group
  38
  39## Functional groups
  40
  41\setchemfig{atom sep=2em}
  42\renewcommand{\arraystretch}{3}
  43\begin{tabularx}{0.5\textwidth}{rlX}
  44  \hline
  45  Alcohols & \ce{-OH} & \chemfig{{\color{blue}R}-OH}\\\hline
  46  Esters & \ce{-OCO-} & \chemfig{{\color{blue}R}-C(=[:-30]O)-[:30]O-{\color{blue}R}}\\\hline
  47  Aldehydes & \ce{-CHO} & \chemfig{{\color{blue}R}-C(-[:-30]H)=[:30]O}\\\hline
  48  Ketones & \ce{-CO-} & \chemfig{C(-[:150]{\color{blue}R})(-[:-150]{\color{blue}R})=O}\\\hline
  49  Carboxylic acids & \ce{-COOH} & \chemfig{{\color{blue}R}-C(=[:-30]O)-[:30]O-H}\\\hline
  50  Ethers & \ce{-O-} & \chemfig{{\color{blue}R}-[:210]O-[:-30]{\color{blue}R}}\\\hline
  51  Amines & \ce{-NH2} & \chemfig{{\color{blue}R}-N(-[:-30]H)(-[:30]H)}\\\hline
  52  Amides & \ce{CO-NH} & \chemfig{{\color{blue}R}-[:30]C(=[:90]O)-[:-30]N(-[:30]H)(-[:-30]H)}\\\hline
  53\end{tabularx}
  54
  55
  56## Isomers
  57
  58* **Structural isomers** - same molecular formula, different arrangement
  59- **Positional isomers** - different position of functional group (affects polarity)
  60- **Chain isomers** - affects boiling point (more branches $implies$ lower boiling point)
  61* **Stereoisomers** - same structural configuration, different orientation  
  62  * **Optical/chiral isomers (enantiomers)** - chiral centre, 4 groups bonded to C, non-superimposable mirror image. Racemic mixture: 50/50 of each enantiomer. Affects optical polarity of light.
  63  * **Geometric isomers** - \ce{C=C} double bond, 2 groups bonded to carbon atoms
  64    + **Cis** - same horizontal plane (symmetrical)
  65    + **Trans** - diagonal (asymmetrical)
  66
  67### Chiral molecules
  68
  69- Not superimposable
  70- Four different groups on C atom
  71- Also called enantiomers
  72
  73\begin{center}\setlength\tabcolsep{1cm}
  74\begin{tabularx}{0.5\textwidth}{cc}
  75  cis & trans \\
  76  \chemfig{[:60]{\text{\color{blue}R$^\prime$}}-C(-[:120]{\text{\color{red}R}})=[0]C(-[:-60]{\text{\color{blue}R$^\prime$}})-[:60]{\text{\color{red}R}}} &
  77  \chemfig{[:60]{\text{\color{blue}R$^\prime$}}-C(-[:120]{\text{\color{red}R}})=[0]C(-[:-60]{\text{\color{red}R}})-[:60]{\text{\color{blue}R$^\prime$}}}
  78\end{tabularx}\end{center}
  79
  80## Flash point
  81
  82Lowest temperature at which the liquid gives off enough vapour to be ignited. Flammable $\implies$ flash point < 37.8 \degree C.
  83
  84## Reactions
  85
  86**Cracking** - split moluecules with heat/pressure/catalyst
  87
  88### Alkanes
  89
  90- Relatively inert
  91- Non-polar solvent
  92- Non-soluble in \ce{H2O}
  93- Combusts in \ce{O2} (forms \ce{CO2 + H2O})
  94- Reacts with halogens (**substitution** of \ce{H})
  95
  96### Alkenes
  97
  98- More reactive than alkanes
  99- **Addition reactions**: \ce{C=C} bond is broken (energy released)
 100- **Addition polymerisation**
 101
 102### Alcohols
 103
 104- Can be formed from haloalkane substitution reaction
 105- **Oxidation** (combustion)
 106- Oxidation state $\propto$ no. of atoms connected to \ce{C}
 107- **Substitution** of functional group, e.g. \ce{ROH + NH3 -> RNH2 + H2O}
 108- Primary alcohols oxidise to aldehydes then carboxylic acids
 109- Secondary alcohols oxidise to ketones
 110
 111### Carboxylic acids
 112
 113- Weak acids
 114- **Hydrolysis**: \ce{RCOOH + H2O <=> RCOO^{-} + H2O^{+}}
 115- Rxn with amines - carboxylic acid + amine $\rightarrow$ ammonium salt $\rightarrow$ amide + water
 116
 117### Esterification
 118
 119- **Condensation reactions** (esterification): \ce{RCOOH + R^{$\prime$}OH -> RCOOR^{$\prime$} + H2O}
 120- This is reversed by **hydrolysis**: ester + water $\rightarrow$ carboxylic acid + alcohol
 121- Polyesters
 122
 123## Summary of reactions
 124
 125\textbf{Combustion:} \ce{C_{$x$} H_{$y$} + $z$O2 -> $x$CO2 + {$\dfrac{y}{2}$} H2O} \quad where $z=x+\dfrac{y}{4}$
 126
 127\textbf{Substitution:} e.g. halogenation/chlorination, catalysed by UV (alkanes) or compounds (alcohols etc.) which creates free radicals (unpaired e-)
 128
 129\textbf{Addition:} \ce{C=C} bond is broken, catalyst is required
 130
 131\textbf{Addition polymerisation:} uses addition to form a polymer
 132
 133\textbf{Condensation polymerisation:} produces \ce{H2O}
 134
 135\textbf{Oxidation:} occurs in alcohols to form aldehydes with catalysts \ce{H+/MnO4- (aq)} or \ce{H+/Cr2O7{2-} (aq)} - see combustion equation
 136
 137\textbf{Cracking:} heat/pressure/catalyst to break molecules