C6.2- Organic chemistry (homologous series) Flashcards
c6.2.1 - c6.2.4 (alkanes, alkenes, alcohol, carboxylic acids)
define an alkane
a saturated hydrocarbon with the formula Cn H2n+2, with the functional group CH^2
acronym to remember first 5 members of alkane/alkene/alcohol/carboxylic acid series
M y E lephant P umps B alloons P ainlessly
Meth- eth- prop- but- pent-
what is the molecular formula for an alkane?
C H
n 2n+2
draw out the displayed formula for propane
H H H
| | |
H-C-C-C-H
| | |
H H Hwhy are alkanes described as saturated hydrocarbons
- They have the maximum amount of hydrogen atoms
since they are joined by single covalent bonds
write out the word equation for complete combustion of alkanes
alkane + oxygen -> water + carbon dioxide
how do alkanes combust in a poor supply in oxygen? (write out the word equation)
alkane + oxygen -> carbon monoxide + carbon + water
define an alkene
an unsaturated hydrocarbon made of ONLY hydrogen and carbon atoms, which contain one double carbon carbon covalent bond
what is the molecular formula for alkenes?
C H
n 2n
draw out the displayed formula for butene
H H H H
| | | |
H-C-C=C-C-H
| |
H H
C4H8
what is different about the first 4 alkene molecules compared to alkanes?
- there is no ‘methene’
- as 2 carbon atoms must be present for a double carbon molecule to be formed
- to produce an alkene
how do alkenes react with plentiful oxygen?
alkene + oxygen -> carbon dioxide + water
SAME AS ALKANE
how do alkenes combust with a limited supply of oxygen?
alkene + oxygen -> carbon monoxide + carbon + water
SAME AS ALKANE
define a functional group
atom/bonds in a molecule that determines the chemical reactions of an organic compound
what allows alkenes to undergo a wider range of reactions? (compared to alkanes)
a double carbon bond functional group
what are addition reactions, and give two examples of them
- when an atom/group of atoms combine with a molecule to form a larger molecule (with NO OTHER PRODUCT)
- reaction with alkenes + bromine water
- reaction with alkenes + hydrogen
what can the addition reaction between bromine water and alkenes be used to detect?
- test for unsaturation (ie. whether hydrocarbon is an alkene or not)
describe how the addition reaction with bromine-water works (not in terms of bonds)
- bromine turns colourless with alkenes
- stays orange-brown with alkanes
- bromine reacts with alkenes, no reaction with alkanes
describe what happens when hydrogen reacts with an alkene, and what the name for that type of reaction is
- called an addition reaction
- an alkane is formed
write down the word equation for an addition reaction with hydrogen and alkene
alkene + hydrogen -> alkane
how do you identify if something is an alcohol (suffix)
ends with ‘ol’
ie. butanol
what is the functional groups of alcohols?
- and what is it called
‘OH’
- called the ‘hydroxyl’ group
what is the molecular formula for alcohols?
C H OH
n 2n + 1
draw out ethanol
and state one thing that is special about how it is drawn out
C H OH
2 5
H H
| |
H--C----C---O----H
| |
H H
- the OH are separate at the side
write out the word equation for the complete combustion of an alcohol
alcohol + oxygen -> water vapour + carbon dioxide
write out the word equation for the incomplete combustion of an alcohol
alcohol + oxygen -> water vapour + carbon monoxide + carbon (ie. soot)
how do you identify if something is part of the carboxylic acid homologous series? (in its name)
ends in ‘anoic’ acid
what is the functional group of a carboxylic acid?
- and whats special about tit
-COOH
C=O double bond at the top
what is the molecular formula for carboxylic acids?
C H COOH
n 2n + 1
why can carboxylic acids take part in different reactions to alkenes and alkanes?
as they have a COOH functional group
draw out the structural formula for methanoic acid
HCOOH
…….O
…….||
H - C - O - H
- remember it only has 1 carbon atom, and all carboxylic acids must have a -COOH functional group (so Cn = C0)
draw out ethanoic acid
.......H....O ........|.....|| H - C - C - O - H ........| .......H
CH COOH
3
draw out butanoic acid
H H H O
| | | ||
H - C - C - C - C - O - H
| | |
H H H
C H COOH
3 7
name the first 4 carboxylic acids
methanoic acid, ethanoic acid, propanoic acid, butanoic acid
how are carboxylic acids made?
when alcohols are oxidised using potassium manganate (VII)
describe an experiment to produce ethanoic acid from ethanol
1) acidify potassium manganate VII with dilute sulfuric acid
2) and add acidified potassium manganate VII oxidising agent to the ethanol
3) colour changes from purple to very pale pink - therefore an acidified solution is made
safety when making a carboxylic acid from an alcohol?
- wear eye protection
- stir reaction carefully (can be violent)
- wear lab coat - potassium manganate can stain clothing + hands (i just thought of this so i’m not 100% sure)
what can a carboxylic acid also be described as?
a weak acid (therefore reacts with metals, bases in the same way)
what do salts produced with a carboxylic acid have the ending of?
ie. ethanoic acid + sodium carbonate
(write out all products of the reaction)
‘oate’
makes:
sodium ethanoate + water + carbon dioxide
