UNIT 11 Organic Chemistry Flashcards

Question

combustion w/ alkanes in EXCESS O2 e.g., methane, COMPLETE CH4 (g) + 2O2 (g) -> CO2 (g) + 2H2O (l)

Answer 1

- in excess oxygen, alkanes burn w/ a blue flame - in COMPLETE combustion, form CO2 and H2O

Answer 2

- in limited O2, alkanes burn w/ yellow/sooty flame - in INcomplete combustion, form CO (+carbon/soot) AND H2O

Answer 3

small chain alkanes: gases at room temp (lower BP) - due to very weak intermolecular forces. WHILE larger chain alkanes are liquids at room temp (higher BP) - due to stronger intermolecular forces + densities between 0.6 and 0.8 g/cm3, so they are less dense than water.

Answer 4

- when an atom attached to a C is replaced by another atom - form haloalkane - a -H atom is replaced by a halogen atom (-Cl) to form 2 new bonds: H-Cl, C-Cl. - due to unreactive nature of alkanes, this is: a SLOW reaction + needs a UV LIGHT CATALYST.

Answer 5

- colourless - insoluble in water, forms 2 layers - less dense than water - small chain alkenes => gases - longer chain length => liquids at room temp [stronger intermolecular forces]

Answer 6

C2H4 + Br2 => C2H4Br2 alkene goes colourless, forms a dihaloalkane while, alkane + Br2 => remains red-brown

Answer 7

the carbon is NOT bonded to the maximum number of atoms (4); [double/triple] bonds can be broken & atoms added - alkEnes & alkynes UNSATURATED while alkanes & alcohols are saturated.

Answer 8

- heating the hydrocarbon molecules to around 600 – 700°C to vaporise them - vapours then pass over a hot powdered catalyst of alumina or silica - process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst, causing thermal decomposition reactions - molecules are broken up in a random way which produces a mixture of smaller alkanes and alkenes - Hydrogen and a higher proportion of alkenes are formed at higher temperatures and higher pressure

Answer 9

- addition with H2O (g) with acid catalyst - the C=C double bond breaks and one hydrogen atom and one OH group is added to the carbons of the double bond - the alkene has one -H atom and one -OH (hydroxyl group) added to form an alcohol

Answer 10

- fuels (flammable) for vehicles - solvents (many substances soluble in short chain alcohols) - for paint varnishes

Answer 11

C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H20 (l)

Answer 12

oxidation, dehydration, substitution, esterification

Answer 13

- Primary alcohols can be oxidised to form aldehydes which can undergo further oxidation to form carboxylic acids - Secondary alcohols can be oxidised to form ketones only - Tertiary alcohols do not undergo oxidation - The oxidising agents of alcohols include acidified K2Cr2O7 or acidified KMnO4

Answer 14

-alcohols undergo dehydration to form alkenes - Alcohol vapour is passed over a hot catalyst of aluminium oxide (Al2O3) powder OR pieces of porous pot or pumice as well as concentrated acid can be used as catalysts

Answer 15

- a type of elimination reaction - a reaction in which a water molecule is removed from a larger molecule

Answer 16

Ethanol (C₂H₅OH) → Ethylene (C₂H₄) + Water (H₂O)

Answer 17

- In the substitution of alcohols, a hydroxy group (-OH) is replaced by a halogen to form an halogenoalkane - can be achieved by reacting the alcohol with: 📍 HX (rather than using HBr, KBr is reacted with H2SO4 or H3PO4 to make HBr that will then react with the alcohol) 📍 PCl3 and heat 📍 PCl5 at room temperature 📍 SOCl2

Answer 18

- condensation reaction between a carboxylic acid and an alcohol to form an ester and a water molecule - carboxylic acid and alcohol are heated under reflux with a strong acid catalyst (such as H2SO4 or H3PO4) - Carboxylic acid + alcohol → ester + water - The reaction is reversible so an equilibrium mixture can be established with all the reactants and products -Esters have sweet, fruity smells

UNIT 11 Organic Chemistry Flashcards

(46 cards)