Chemistry - U4 AOS1

Number of covalent bonds that can be formed by carbon

4

Shape of carbon bonded with 4 other atoms

Tetrahedral

Shape when carbon has a double bond

Planar

Shape when carbon has a triple bond

Linear

Factors contributing to relative bond strength

Bond length, difference in electronegativity of atoms involved and size of atoms

Order of decreasing electronegativity

FONCl

Alkane

CnH2n+2

Alkene

One degree of unsaturation(CnH2n)

Cyclohexane

Saturated cyclic hydrocarbon(C6H12), no terminal carbon

Benzene

Unsaturated aromatic compound(C6H6)

• delocalised e- are shared equally between C atoms

• very stable structure

Haloalkanes

Contains one or more halogens(F,Cl,Br,I)

• often represented by X

• C-X bonds are polar

Primary amine

• contain amino group NH2

• generally derived from ammonia

Amides

• contain amide group (CONH)

• forms when a carboxyl group reacts with an amine group

• sometimes known as peptides

Acohols

Contains a hydroxyl functional group (OH)

Primary alcohol

Hydroxyl group is bonded to carbon with only 1 alkyl group/terminal carbon.

Secondary alcohol

Hydroxyl group is bonded to carbon that is bonded to 2 alkyl groups.

Tertiary alcohol

Hydroxyl group is bonded to carbon that is bonded to 3 alkyl groups.

• aren’t very reactive since very stable

Alkyl group

Contains only carbon and hydrogen atoms (e.g methyl -CH3)

Aldehyde

Contains a carbonyl group(C=O) on a terminal carbon therefore aldehyde functional group is CHO.

• polar

Ketone

• contains a carbonyl group(C=O) attached to 2 other alkyl groups

• attached to a non-terminal carbon

Carboxylic acid

• contains a carboxyl group(-COOH) on a terminal carbon

• carboxyl group is acidic though carboxylic acids are weak

• polar

• highest priority in naming

Ester

• fruity flavours/smells

• contains an ester functional group(-COOC-)

Methyl

CH3

Ethyl

CH3CH2

• if both are present, then write in alphabetical order

Highest to lowest priority in naming - Functional groups

Carboxylic acid, ester, amide, aldehyde, ketone

Structural isomers

Molecules with the same molecular formula but different spatial arrangement of atoms

Instantaneous dipole

Partial positive and negative charge that suddenly appears in an atom or molecule due to the random movement of electrons

Dispersion forces increase when…

• length of carbon chain increases

• branching is reduced

• increased saturation

Atom economy

Molar mass of desired products divided by molar mass of all reactants given as a percentage conversion.

Benefits of using catalysts in organic synthesis

• improved selectivity(eliminates unwanted products)

• lower energy consumption

• renewable source utilisation

• safer reactions

• longer catalyst lifetime

Substitution reaction

Chemical reaction where an atom or group of atoms in a compound, are replaced by another atom or group of atoms. e.g.

alkane + halogen —(UV/heat)—> haloalkane + hydrogen halide

primary haloalkane + hydroxide ions/water —(heat)—> primary alcohol + halide salt

primary alcohol + ammonia(NH3) —> primary amine + water

Addition reaction

Chemical reaction where one molecule combines with another to form a larger molecule with no other products.

• involves alkenes(double bond is replaced with a single carbon bond)

• one product is formed, good atom economy

• polymerization(heat and catalyst), breaks double bond to form single

e.g.

alkene + hydrogen halide(HCl(g)) —> haloalkane

alkene + hydrogen —(Ni/heat)—> alkane, hydrogenation

alkene + halogen —> dihaloalkane, e.g. bromination if halogen is Br

alkene + water vapour —(H3PO4(l)/heat/pressure)—> alcohol, hydration

Oxidation of alcohols

primary alcohol —(H^+/MnO4^- or H^+/Cr2O7²-)→ aldehyde —(same)→ carboxylic acid

• secondary alcohols can be oxidised to form a ketone

Esterification reaction

Chemical reaction between organic compounds that forms at least one ester and water as products.

• a type of condensation reaction

e.g.

carboxylic acid + alcohol —(conc. H2SO4/heat)—> ester + water

Condensation reaction

Chemical reaction in which two or more molecules combine and release a water molecule.

Hydrolysis

Chemical reaction in which water reacts with a larger molecule to break it into two or more smaller molecules.

• reverse reaction of an esterification reaction

• reverse of condensation reactions(water is a reactant)

• for proteins and polypeptides(amides), products are amino acids and peptides

• enzymes for reaction to occur for protein reaction

e.g.

ester + water(l) → carboxylic acid + alcohol

Monosaccaride

Type of sugar e.g. glucose, fructose and galactose

Polysaccharide

Polymers produced from the condensation of multiple monosaccharides including starch and glycogen.

• group term is carbohydrates

Disaccharide

Product from the condensation of two monosaccharides.

• building blocks of polysaccharides

a-glucose + b-fructose —> sucrose + water

a-glucose + a-glucose —> maltose + water

Glycosidic link

C-O-C covalent bonds within and between sugar monomers. Also called an ether link.

Triglyceride

Type of lipid found in living organisms. Made up of glycerol and 3 fatty acids. Contains 3 ester(-COOC-) links.

Amide link

Condensation of amino acids to produce proteins. One link for every molecule of water.

Qualitative signs of a chemical reaction(COBALT)

• colour change

• odour changes

• bubbles appearing

• appearance or disappearance of solid

• light or sound produced

• temperature change(qualitative)

Bromine water test

Detects presence of carbon-carbon double bonds, alkenes from alkanes.

Unsaturated/double bond = colourless

Saturated/single bond = orange

Acidified permanganate test

Test for presence of carbon-carbon double bonds.(KMnO4 and H^+)

Unsaturated = brown precipitate

Saturated = purple colour/no colour change

Acidified potassium dichromate test

Test for presence of primary or secondary alcohol as well as aldehyde(after Tollens test). Detects -OH, hydroxyl group.

Lucas test

Test for presence of primary, secondary or tertiary alcohol.

If cloudy then present.

Esterification(test)

With H2SO4(l) catalyst, smell detects ester.

Acid-base indicator test

Test for presence of acid.

Pure substance

Compound of one type of element or compound that cannnot be separated into two or more substances by physical means.

• has experimentally determined melting points

• melting point determines purity of solids

• if impure, melting point is lower or has a broader range

Fractional distillation

Technique used to separate iiquids with a narrow range of boiling points.

• presence of impurities results in higher boiling point since introduces different intermolecular forces