update practice exams

diff --git a/chem/organic-2.md b/chem/organic-2.md
index c0fadf2c65b10361e146a44c4f290bbc7968d564..f47f267bb321b768a79ff6a6fcbd51b0be95c41d 100644 (file)
--- a/chem/organic-2.md
+++ b/chem/organic-2.md
@@ -4,6 +4,7 @@ header-includes:
 - \usepackage{mhchem}
 - \usepackage{chemfig}
 - \usepackage{tabularx}
+- \usepackage{gensymb}
 ---
 
 # Organic Chemistry
@@ -48,18 +49,26 @@ Alkynes: \ce{C_{$n$} H_{$2n-2$}}
   Carboxylic acids & \ce{-COOH} & \chemfig{{\color{blue}R}-C(=[:-30]O)-[:30]O-H}\\\hline
   Ethers & \ce{-O-} & \chemfig{{\color{blue}R}-[:210]O-[:-30]{\color{blue}R}}\\\hline
   Amines & \ce{-NH2} & \chemfig{{\color{blue}R}-N(-[:-30]H)(-[:30]H)}\\\hline
-  Amides & \ce{-CONH2} & \chemfig{{\color{blue}R}-[:30]C(=[:90]O)-[:-30]N(-[:30]H)(-[:-30]H)}\\\hline
+  Amides & \ce{CO-NH} & \chemfig{{\color{blue}R}-[:30]C(=[:90]O)-[:-30]N(-[:30]H)(-[:-30]H)}\\\hline
 \end{tabularx}
 
 
 ## Isomers
 
-* **Structural isomers** - same molecular formula, different arrangement  
+* **Structural isomers** - same molecular formula, different arrangement
+- **Positional isomers** - different position of functional group (affects polarity)
+- **Chain isomers** - affects boiling point (more branches $implies$ lower boiling point)
 * **Stereoisomers** - same structural configuration, different orientation  
-  * **Opotical isomers** - chiral centre, 4 groups bonded to C, non-superimposable mirror image
+  * **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.
   * **Geometric isomers** - \ce{C=C} double bond, 2 groups bonded to carbon atoms
-    + **Cis** - same horizontal plane
-    + **Trans** - diagonal
+    + **Cis** - same horizontal plane (symmetrical)
+    + **Trans** - diagonal (asymmetrical)
+
+### Chiral molecules
+
+- Not superimposable
+- Four different groups on C atom
+- Also called enantiomers
 
 \begin{center}\setlength\tabcolsep{1cm}
 \begin{tabularx}{0.5\textwidth}{cc}
@@ -68,6 +77,10 @@ Alkynes: \ce{C_{$n$} H_{$2n-2$}}
   \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$^\prime$}}}
 \end{tabularx}\end{center}
 
+## Flash point
+
+Lowest temperature at which the liquid gives off enough vapour to be ignited. Flammable $\implies$ flash point < 37.8 \degree C.
+
 ## Reactions
 
 **Cracking** - split moluecules with heat/pressure/catalyst
@@ -106,3 +119,19 @@ Alkynes: \ce{C_{$n$} H_{$2n-2$}}
 - **Condensation reactions** (esterification): \ce{RCOOH + R^{$\prime$}OH -> RCOOR^{$\prime$} + H2O}
 - This is reversed by **hydrolysis**: ester + water $\rightarrow$ carboxylic acid + alcohol
 - Polyesters
+
+## Summary of reactions
+
+\textbf{Combustion:} \ce{C_{$x$} H_{$y$} + $z$O2 -> $x$CO2 + {$\dfrac{y}{2}$} H2O} \quad where $z=x+\dfrac{y}{4}$
+
+\textbf{Substitution:} e.g. halogenation/chlorination, catalysed by UV (alkanes) or compounds (alcohols etc.) which creates free radicals (unpaired e-)
+
+\textbf{Addition:} \ce{C=C} bond is broken, catalyst is required
+
+\textbf{Addition polymerisation:} uses addition to form a polymer
+
+\textbf{Condensation polymerisation:} produces \ce{H2O}
+
+\textbf{Oxidation:} occurs in alcohols to form aldehydes with catalysts \ce{H+/MnO4- (aq)} or \ce{H+/Cr2O7{2-} (aq)} - see combustion equation
+
+\textbf{Cracking:} heat/pressure/catalyst to break molecules