Introduction to Organic Chemistry PDF

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Summary

Organic ChemistryCarbon Group 14  4 valence electrons  Carbon can bond to another atom in a number of different combinations  Means that C can bond to other atoms in a lot of different conformations to form all kinds of structures  Covalent bond = bonding Electrons spend most of their time betw...

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Organic Chemistry Carbon         

Group 14 4 valence electrons Carbon can bond to another atom in a number of different combinations Means that C can bond to other atoms in a lot of different conformations to form all kinds of structures Covalent bond = bonding Electrons spend most of their time between the nuclei & the nuclei stay close together because they are attracted by the electrons Electron configuration : 1s2 2s2 2p2 Valence shell configuration : 2s2 2p2 Electronegativity : 2.5 Expected bond type : Covalent and polar covalent

Formula in Organic Chemistry

Sigma Bonds     

End to end overlap bond is sigma bond. Orbitals overlap as two atoms approach Electrons of one atom attracted to nucleus of the other This continues until the repulsion between nuclei outweighs this attraction End to end overlap bond is sigma (σ) bond.

Bonding of Carbon  

Carbon has 2 unpaired electrons A widely used approach based on Valene Bond theory is hybridisation of atomic orbitals

Sp3 Hybridisation   

Promoting a 2s electron into an empty 2p orbital gives 4 unpaired electrons (2s 1 2p3) Methane would have four bonds but 3 of one type and one of another – these would be of different lengths All four bonds in methane are equal so the bonding atomic orbitals of carbon must be equivalent

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The s and p orbitals are mixed to form hybrid orbitals One s and three p orbitals are mixed, so this process is called sp 3 hybridisation

Sp2 Hybridisation      

Carbon that is only bonded to 3 atoms Ethene is a planar molecule (HCH angle 121.3 o). These three hybrid orbitals can form three σ bonds sp2 hybridisation (one s and two p orbitals) gives a bond angle of 121.3° These three hybrid orbitals can form three σ bonds The two pure p orbitals (of the 2 C atoms) can overlap sideways to form a p bond

Benzene    

Benzene is a planar molecule Each carbon atom is sp2 hybridised (cf ethene) 6 electrons in pure p orbitals capable of overlapping Get delocalisation over the ring

Sp Hybridisation   

Can be explained by mixing one s orbital with one p orbital to obtain two sp hybrid orbitals Two pure p orbitals are left over per C – so two p bonds Each carbon atom forms two s bonds and two p bonds

Properties of Organic Compounds    

Physical and chemical behaviours are heavily influenced by polarity Most organic compounds are not soluble in water Organic compounds containing oxygen or nitrogen are somewhat soluble due to their electronegative atoms forming H bonds with water Many organic compounds undergo combustion and burn vigorously in air

Polarity of Organic Compounds  

A covalent bond between two carbon atoms is non-polar because the electrons are shared equally Most of the elements found in organic compounds are more electronegative than carbon (except H)

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Polarity of a molecule is determined by the polarity of its bonds and the structure of the molecule C-Cl bond is polar, but CCl4 is a non-polar molecule because it has a symmetrical arrangement of polar bonds that cancels out the dipoles

Classes of Organic Compounds 1. Aromatic (Contain cyclic conjugated double bond system with 4n + 2 π electrons) 2. Aliphatic (All other compounds without such ring system) Functional Groups

Reactions of Carbon Compounds      

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Oxidation - When carbon atoms are oxidised they often form additional bonds to oxygen Reduction - When carbon atoms are reduced they often form additional bonds to hydrogen Substitution - Exchange of one atom in a molecule with another atom or group of atoms Elimination - A single reactant is split into two products Addition - Two reactants add together to form a single product (opposite to elimination) Homolytic -1 electron transferred to each atom -Formation of radicals Heterolytic -Two electrons transferred -Formation of ions...