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Flashcards in Organic Chemistry Deck (22):
1

What is a hydrocarbon

Compound that contains hydrogen and carbon ONLY

2

What is an ALKANE

Saturated hydrocarbon

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What is ALKENE

UnSaturated hydrocarbon

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Hydrocarbon properties change as the chain gets longer

Shorter carbon chain- more runny a hydrocarbon is the less viscous (gloopy) it is

More volatile it is ie they have lower boiling point

More flammable

The properties of hydrocarbons affect how they’re used for fuels eg short hydrocarbon chains with lower boiling points are used as bottled gas stored under pressure as liquids in bottles

5

How does separation occur in fractional distillation

The crude oil (not useful) is heated and evaporated to vapour. The gas enters a fractionating column . In the column it’s hot at the bottom and gets cooler as you go up. The longer hydrocarbons have high boiling points they condense at the bottom. The different hydrocarbon vapours cool and condense as they rise up the fractionating column at different temperatures because they have different boiling points (condensation points) and the vapour condenses to a liquid at their boiling point

6

Cracking

The global demand for fuel is very high (smaller hydrocarbons) meaning that there is a shortage of smaller hydrocarbons and an excess of larger hydrocarbons(bitumen surfacing roads). Cracking is the processs of larger less useful molecules and breaking them into smaller higher demand molecules using heat! Cracking is THERMAL DECOMPOSITION reaction because large alkanes are heated to a vapour and broken up(decomposed) into smaller molecules! The first step is it to heat long chain hydrocarbons to vaporise them(turn into a gas) then the vapour is passed over a hot powdered ALUMINIUM OXIDE CATALYST. The long-chain molecules split apart on the surface of the specks of catalyst- CATALYTIC CRACKING !!!!! You can also crack hydrocarbons if you vaporise them , mix with steam and then heat to very high temp this is THERMAL CRACKING! During cracking a mixture of ALKANE AND ALKENE IS ALWAYS MADE !!!!!!

7

Reaction of alkene- with hydrogen

Hydrogen can react with an unsaturated alkene to open up the double bond. And form a saturated alkane! This is called HYDROGENATION and occurs at 150 degrees with a NICKEL CATALYST

8

Reaction of alkene - with oxygen

Alkene can react with oxygen in combustion (burning) reactions just like alkanes. However we don’t generally combust alkenes on purpose for two reasons
Alkenes burn with smokey flames due to incomplete combustion (soot is made)
Alkenes are more useful as starting materials for making polymers, alcohols, medicines and other useful materials

9

Reaction of alkene - with halogens

Alkenes will also react in ADDITION REACTIONS with halogens such as bromine chlorine and iodine. The halogen atoms are added across the unsaturated double bond to make only single carbon bonds

10

Reaction of alkene - with water (steam)

Alkenes react with water by an ADDITION REACTION whereby the OH and H of water are added across the double carbon bond . High temperatures and high pressure are required with a PHOSPHORIC ACID CATALYST

11

Reaction of alcohol - with water

Alcohols possess covalent bonds that do not break easily so DO NOT REACT WITH WATER! Other than to dissolve easily in it eg ethanol is dissolved in vodka / wine etc . Solution formed is neutral (ph 7)

12

Reaction of alcohol - with oxygen (complete combustion)

All alcohols burn in air producing co2 and water

13

Reaction of alcohol - with oxygen (mild oxidation)

In combustion , alcohol molecules are blasted apart vigorously to form CO2 and H2O. However a mild oxidising agent will gently add oxygen (or remove hydrogen) from a molecule without breaking it apart . When alcohols are oxidised they produce CARBOXYIC ACIDS! The most common example is when whine containing Ethanol is oxidised by the hair to make vinegar (ethanoic acid) eg when methanol is oxidised it makes methanoic acid and when ethanol is oxidised it makes ethanoic acid

14

Reaction of alcohol - with sodium metal

Sodium metal will react with alcohols in a similar way to when sodium reacts with water producing HYDROGEN gas and a basic solution

15

Uses of alcohols

Alcohols are very good solvents and are used to dissolve perfume molecules and medicines that are not soluble in water . Ethanol is the main alcohol in alcoholic drinks . Fermentation

Conditions for fermentation- yeast, no oxygen , 37 degrees
Sugar uses a yeast enzyme to make carbon dioxide and the ethanol needed . The carbon dioxide will make bubbles


You would put warm water yeast and sugar in a conical flask with a fermentation lock

16

Alcohol functional group

O-H

17

Carboxylic acid functional group

COOH



Their names end in ‘anoic acid’ and start with the normal meth/eth/prop/but

18

Reaction of carboxylic acid - with water

Carboxylic acids also dissolve in water . When they dissolve they ionise and release H+ resulting in an acidic solution but because they don’t ionise completely they just form weak acidic solutions .

19

Reaction of carboxylic acid - with carbonate

ACID+CARBONATE = SALT+WATER+CO2
You would see bubbles of gas

20

Reaction of carboxylic acid - with alcohol ESTERRRRRR!!!!!!!!

ALCHOL+Carboxylic acid= Ester and water
Concentrated Acid catalyst needs to be present eg (concentrated sulfuric acid)

Esters have sweet Smells eg perfume or food flavouring

21

What is the ester functional group ?

COO

22

What is a polymer

A long molecule of small molecules called monomers