Chapter 16 (16.3-16.8) Nomenclature Flashcards
what are the three types of hydrocarbons
alkanes, alkenes, alkynes
characteristics of a homologous series
same functional group
same general formula
same chemical properties
Consecutive members differ by CH2
boiling and melting points increases down a homologous series
common methods of preparation
Viscosity increases
Flammability decreases
What is a functional group (definition)
An atom or group of atoms in a molecule that dictates how the compound will react
which hydrocarbon is unsaturated
alkene, alkyne
Are alkenes or Alkanes more reactive
why
Alkenes - double bond easier to break
what is the general formula of alkanes
CnH2n+2
eg:- carbon = 7
then hydrogen = 2(7)+2 therefore 16
C7H16
functional group of alkane
single bond between carbons
properties of alkanes
insoluble in water
The boiling point of alkanes increases with increasing molecular weight.
The melting point of alkanes increases with an increase in molecular weight.
naming alkanes
1) select longest chain (straight, L shaped)
2) number closest to the branch
3) all other groups not part of the longest chain should be taken as a branch
4) if there is more than one group present as a branch then written as di,tri etc. and branches are named in alphabetical order eg ethyl, methyl. ethyl comes first
what is methane
ch4
what is ethane
c2h6
what is propane
c3h8
what is butane
c4h10
combustion reaction of alkanes
Alkane + oxygen –> co2 + h2o
eg: CH4 + 2o2 –> CO2 + 2H2O
What is a substitution reaction
Example
One atom or a group of atoms is replaced by another atom or group of atoms
Eg: Photochemical Reaction
photochemical reaction of alkane
occurs only under presence of light
Alkane + Halogen —–light—–> Alkyl-Halide + Acid
CH4 + Cl2 —–light—–> CH3Cl + HCl
What does the light do in a photochemical reaction
provides the activation energy required for the reaction
What happens as the amount of chlorine increases in photochemical reaction
More and more hydrogen atoms are substituted by chlorine atoms
properties of alkynes
have one less hydrogen than their alkane (methane ch4 /methyl ch3)
general formula of alkenes
CnH2n
what is the functional group of alkenes
double bond between the carbon
naming alkenes
1) select longest chain
2) naming starts closest to the double bond
properties of alkenes
Unsaturated (reactive) due to double bond between the 2 carbons
known as olefins as when they react with halogens they produce oil.
colorless
odourless
insoluble in water
The boiling points of the compounds increase as the number of carbon atoms in the compound increases.
What is cracking
Process of breaking molecules into smaller ones
What is Zeolite
Hot catalyst used in cracking
cracking of alkanes and alkenes
1) long chain alkane —heat,pressure,catalyst—-> alkene + hydrogen
2) long chain alkane —heat,pressure,catalyst—-> short chain alkane + alkene
no.1 eg: c5h12 (pentane) -h,p,c—> c5h10 + h2
no.2 eg: c5h12 (pentane) -h,p,c—> c2h6 + c3h6
Why is cracking performed
Make the best use of petroleum to meet demand
Gives alkenes, which aren’t found in petroleum
combustion reaction of alkenes
Alkene + oxygen —-> carbon dioxide + water
What is an addition reaction
Turns unsaturated alkenes into a saturated compound.
ONLY YILEDS ONE PRODUCT
2 types of addition reactions
hydrogenation of alkene
Alkenes + Hydrogen –> Alkanes
Hydration of alkenes
Alkenes + H2O –h, p, acid c–> Alcohols
hydrogenation of alkene
(Conversation from alkene to alkane)
c2h4 + h2 –h,p,c—> c2h6
hydration of alkene
c2h4 (ethene) + H2O <—-300c, 60-70 pressure, phosphoric acid—–> C2H5OH
test for unsaturation
bromine water + alkane —> no colour change (remains orange)
indicating that it is saturated
bromine water + alkene —-> orange-brown to colorless
indicating that it is unsaturated as bromine can be added
what are isomers
compounds that have the same molecular formula but different structural formula
Alkene isomers
1) branch
where in the branching in the structure is different
2) unbranch
where its the longest chain but placement of the double bond is different
general formula and functional group of alcohol
are they a hydocarbon
functional group: OH
general formula: CnH2n+1OH
Not a hydrocarbon
2 methods to yield alcohol
1) biological method. anaerobic respiration of yeast yields alcohol
C6H12O6 —–> 2C2H5OH + 2CO2
2) chemical method, hydration of ethene. C2H4 + H2O (gas) <—-300c, 60-70Pa—–> C2H5OH
combustion of Alcohol
C2H5OH + O2 —-> CO2 +H2O
highly exothermic reaction, hence alcohol is used as a fuel
oxidation of alcohol
C2H5OH + [O] —-> CH3COOH
alcohol on oxidation form carboxylic acid
what is Carboxylic Acid’s functional group and general formula
Are they a hydrocarbon?
an acid that is made of carbon, hydrogen and oxygen
functional group: COOH
general formula: CnH2n+1COOH
Not a hydrocarbon
formation of carboxylic acid
Biological method: fermentation, while making alcohol expose it to the air for it to form carboxylic acid, through oxidation, adding bacteria could also form carboxylic acid
Using alcohol and oxidizing agent:- use potassium permanganate or potassium dichromate as an oxidizing agent. this agent will bring about oxidation on alcohol
potassium permanganate
MnO4 —> Mn2+
potassium dichromate
CrO7^2- —-> 2Cr2+
reactions of carboxylic acid
carboxylic acid + metal —> metal carboxylate + h2
carboxylic acid + metal oxide/hydroxide —> metal carboxylate + H2O
CH3COO- always gains electrons
esterification
carboxylic acid + alcohol —-> ester + h2o
eg ethanoic acid + methanol —-> methyl-ethanoate + h2o
how to name esters
alcohol + yl, carboxylic acid + ate
How are aklanes, alkenes, alcohol and carboxylic acids linked?
Alkanes - obtained from petroleum/occur naturally
Alkenes - cracking Alkanes
Alcohols - Alkenes reaction with water
Carboxylic acids - Oxidising Alcohols
what is butanol oxidised by
Butan-1-ol is oxidised by acidified potassium manganate
which naturally occurring compounds contain the ester linkage
fats / vegetable oils
what is meant by the term fermentation
sugar (glucose) changed to alcohol (ethanol)
c6h12o6 + 2c2h5oh + 2co2
catalysed by enzymes
What type of compound are vegetable oil and biodiesel?
esters
What other useful product is made from vegetable oil by heating it with aqueous sodium hydroxide?
soap
why is biodiesel better for the environment than petroleum-based diesel
both produce carbon dioxide and emit it into the environment
but growing plants is needed to make bio fuels and plants remove carbon dioxide from the air
when writing an esters structural formula which compounds structual formula comes first
carboxylic acid-coo-alcohol
eg propyl ethanoate
ch3-coo-c3h7
How could you show that butanol made from petroleum and biobutanol are the same
chemical?
see if they boil at the same temp
2 conditions needed for the fermentation of glucose
Yeast
Anaerobic respiration - no oxygen
Why does the concentration of ethanol produced by fermentation not exceed 15%
is this an adv or disadv
Disadv - If concentration exceeded 15% it would kill the yeast and hence never exceeds that.
Another disadvantage of fermentation
slow rate of reaction
