10 - Organic Chemistry

10.1 - Basics 10.2 - Functional Group Chemistry 20.1 - Organic Reactions 20.2 - Synthetic Routes 20.3 - Stereomerism

Organic Chemistry

focuses on compounds containing carbons, biological molecules like simple sugars to nucleic acids, fossil fuels like coal and natural gas, synthetic materials like nylon and Lycra, domestic and industrial products like paints and detergents.

Organic Compound

a compound containing carbon, most of the time also hydrogen in a covalent bond. Oxygen, nitrogen, chlorine, sulfur are often present as well.

Why is carbon important?

Carbon forms four strong covalent bonds with other elements, namely hydrogen. Carbon is also capable of catenation, link to itself forming chains or rings.

Homologous series

families of compounds with the same functional group, similar chemical and physical properties that can be represented by the same general formula. For instance, Alkanes are represented by the general formula C_nH_2n+2, and each successive member increases by a fixed amount of molecular mass.

Homologous series and Physical properties

As successive members of a homologous series differs by CH₂ groups they possess longer carbon chains and exhibit gradual trends in their physical properties.

Boiling point increases as the molecular weight and size increase, hence induced dipoles cause stronger London dispersion forces between molecules, requiring more energy for transition between liquid and gas. The increase is steeper initially as the increased chain length is relatively greater for small molecules. CH₄ is a gas at room temp and C₈H₁₈ is a liquid,

Density increases as molecular weight increases, hence more mass per unit volume.

Viscocity increases as molecular weight increases and larger molecules experience more resistance to flow due to more complex structure.

Homologous series and Chemical properties

Homologous series show trends in chemical properties as they have the same functional group. If the traits of a functional group are know the properties can be predicted for all members of a series.

Reactivity: Alcohols with -OH functional group can be oxidized to form organic acids, the -COOH functional group in Carboxylic acids is responsible for acidic properties

Functional group

an atom or group of atoms attached to a carbon atom in a molecule that provides a compound with certain chemical properties, denoted by R - rest of the molecule

Organics and Empirical formulae

The empirical formula shows the simplest whole number ratio of the atoms it contains, it can be derived from percentage composition data.

Organics and Molecular formulae (P 467)

The molecular formula shows the actual number of atoms of each element, if the molecular formula is a multiple of the empirical formula and Molar mass, M, the relationship M = (molar mass of empirical formula)_n can be applied.

Structural formula

a representation of the molecule showing how atoms are bonded to each other, show bonds and bond angles.

Stem identifies the number of carbon atoms in longest chain:

Meth- = 1C, Eth- = 2C, Prop- = 3C, But- = 4C, Pent- = 5C, Hex- = 6C, e.g: Methane = CH4, Hexane = C6H14.

Mnemonic: Methhead Ethel Propels Butterfly Pentagram Hexes

Suffix endings and Nomenclature

suffix identifies, class, functional group and general formula

Suffix	Class	Functional Group	General Formula
ane	alkane	no functional group	CnH2n+2
ene	alkene	alkenyl	CnH2n
yne	alkyne	alkynyl	CnH2n-2
anol	alcohol	hydroxyl	CnH2n+1OH
oxylakane	ether	ether	R - O - R’
anal	aldehyde	aldehyde/carbonyl	R - CHO
anone	ketone	carbonyl	R - CO - R’
anoic acid	carboxylic acid	carboxyl	CnH2n+1COOH
anoate	ester	ester	R - COO - R’
anamide	amide	carboxyamide
anamine	amine	anamine
anenitrile	nitrile	anenitrile
benzene	arene	phenyl

Position of a Functional group

The position of a functional group is shown by a number between dashes inserted before the functional group ending, the number refers to the carbon atom to which the functional group is attached, chain is numbered starting at the end that will give the smallest number to the group

Alcohol functional group

Alcohol functional group involves an oxygen atom bonded to a hydrogen atom, -OH, and a carbon atom which is part of a larger organic. R-OH.

Alkyl

An alkyl grou[ is formed by remove one hydrogen atom from an alkane chain, and so stem changes from -ane to -yl. The letter R is used to discuss an unspecific alkyl group.

E.g.: Methane CH4 - H = Methyl CH3

Aromatic compound

Aromatic compounds contain a benzene ring, C6H6,

Saturated Reactant

Compounds containing only single bonds, like alkanes

Unsaturated reactant

Compounds containing double or triple bonds, like alkenes, arenes

Aliphatic reactant

Aliphatics are saturated or unsaturated compounds without a benzene ring, like alkanes or alkenes

Arene reactant

Arenes are unsaturated compounds containing a benzene ring, like benzene or phenol

Electrophile

A species missing an electron hence attracted to parts of molecules that are electron-rich, electrophiles are positive ions or have partial + charges, like H+

Nucleophile

An electron-rich species hence attracted to parts of molecules which are missing electrons, nucleophiles have a lone pair of electrons and may have negative charges, like Cl-.

20.2 START

Nucleophilic Substitution

In nucleophilic substitution reactions a nucleophile species with a lone electron pair replaces the functional group of within an electrophile molecule.