Analysis of the Earth and Environment Lecture 12: Carbon and Organic chemistry Flashcards
What is the main type of chemical bonding used in organic compounds
Covalent
List some organic compounds
alkanes, alkenes, alkynes, alcohols, aldehydes, ketones, organic acids, benzenes, amines
Describe a carbon atom
6 Neutrons
6 Protons
6 Electrons
Four electrons in shell 2
Therefore 4 electrons available to form covalent bonds with other atoms
Describe covalent bonding in carbon atoms
The four different covalent bonds spread as far apart from each other as they can giving 109.5o angles between them.
Giving a tetrahedral shape, with the carbon atom in the centre
List the allatropes of carbon
Carbon atoms have the potential to bond together in the form of giant structures. Different configurations of one element are called allotropes.
Diamond
Graphite
Graphene
Fullerenes (/Buckminsterfullerene)
Nanotube
Describe the structure of diamond
Each carbon is covalently bonded to four other carbons.
Produces a giant lattice structure
Bonds are difficult to break
Makes an extremely hard material – used for drill bits
Describe the structure of Graphite
Carbon is bonded in layers
Only three of the four available electrons contribute to covalent bonds between the carbon atoms - hexagonal configuration
Weak attractions between each layer are easily broken. (Van Der Waals)
Uses of graphite?
Largest exporter of Graphite
Because the layers of carbon slip smoothly over each other graphite is used as…….
Pencil “lead”
Dry lubricant for machine parts
Because there is an unbound electron, graphite conducts electricity so used as………
Electrodes
China is the largest exporter producing 75-80% of the world’s graphite.
Describe the structure of Graphene
structure is similar to sheets graphite structure however it is a one atom thick sheet of carbon atoms
Looks like sheet of honeycomb
Describe uses and characteristics of graphene
200x stronger than steel
Thin and lightweight
High electrical conductivity
High thermal conductivity
Very high transparency
Describe the structure of Buckminsterfullerene
Carbon atoms covalently bonded in “cage” formation - resemble a football made of twenty hexagons and twelve pentagons
Simplest fullerene is 60 carbon atoms
Can be engineered to contain other types of molecules inside eg. to deliver drugs to specific parts of the body.
Define a hydrocarbon
A compound which contains only hydrogen and carbon
Carbon atoms have 4 sites which can bind to other atoms
The simplest hydrocarbon is methane(CH4), which is part of the alkane group
Define alkanes
Compounds which follow a generic formula are called a “homologous series”
The generic formula for alkanes is Cn H2n+2
Meaning CH4
C2H6
C3H8
C4H10
C5H12
Each single bond supplied by a carbon atom attaches to another carbon or a hydrogen atom
Alkanes only contain SINGLE BONDS – such compounds are termed “SATURATED” hydrocarbons.
List the Alkanes and their chemical composition
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Pentane C5H12
Hexane C6H14
Heptane C7H16
Octane C8H18
Nonane C9H20
Decane C10H22
Describe the use of alkanes as fuels
The shorter the carbon chain the lower the boiling point ie. gas at ambient temperatures
The shorter the carbon chain the cleaner the alkane will burn (without producing carbon solids forming soot)
Alkanes are the energy providing compounds found in CRUDE OIL & NATURAL GAS
Major component of natural gas - formed by anaerobic decay of organic matter over millions of years. Methane is piped from gas fields
Describe how methane is produced and harvested
Major component of natural gas - formed by anaerobic decay of organic matter over millions of years. Methane is piped from gas fields across vast distances for domestic and industrial heating.
Also produced by decay of waste in landfills – a process which is harnessed in anaerobic digesters.
Traces of methane gas occur in the Earth’s atmosphere produced primarily by organisms such as Archaea found in the gut of cows.
Describe the burning/combustion of alkanes in oxygen
When alkanes burn in plenty of oxygen they produce carbon dioxide, water and heat energy.
Eg. Propane
C3H8 + 5O2 3CO2 + 4H2O + energy
List the Alkyl branches
Methyl CH3-
Ethyl C2H5-
Propyl C3H7-
Butyl C4H9-
What is a Haloalkane
these compounds, some of the hydrogen atoms are substituted with halogen atoms (Group 17 elements)
Examples;
fluorine fluoroalkanes
chlorine chloroalkanes
Define alkenes
Alkenes are hydrocarbons which contain a C=C double bond
Alkenes are termed UNSATURATED because it is not formed entirely by single covalent bonds
Describe cracking and its word equation
To convert a less useful alkane from crude oil into a useful alkene requires the process called cracking
long chain alkane alkene + octane
(heat & catalyst)
Are Alkenes good fuels
Alkenes do NOT make good fuels as they are smoky when they burn.
Their value is in the manufacture of polymers.
When the double bonds are broken, it opens up bonds for further units to join.
Very long chain compounds can be made by this process called polymerisation.
Describe alcohol
Functional group is a hydroxyl group (-OH)
Homologous series
Methanol CH3OH (formerly known as methyl alcohol)
Ethanol C2H5OH (“alcohol” found in alcoholic beverages)
Propanol C3H7OH (formerly known as isopropyl alcohol)
Describe Aldehydes and Ketones
Functional group is a carbonyl group (C=O)
Removing two hydrogens from a carbon in a chain and replacing them with C=O gives a series of compounds with different properties. Depending on which carbon the C=O is attached to, they are classed as ketones or aldehydes.
In particular, it changes the range of substances that the organic compound can dissolve eg. propanone is the chemical name for the ketone more commonly called acetone which is versatile solvent.
Describe organic acids
The functional group is called a carboxyl group -COOH
Homologous series
Methanoic acid HCOOH (formerly called formic acid)
Ethanoic acid CH3COOH (formerly called acetic acid)
Propanoic acid CH3CH2COOH (smells like body odour!)
What does aromatic mean in chemistry?
AROMATIC in chemistry means hydrocarbon contains a BENZENE RING
Describe a Benzene
ring of six carbon atoms and six hydrogen atoms attached. The chemical formula for benzene is C6H6
Only one hydrogen per carbon
The bonds between the carbons are a hybrid between a single and a double bond
Functional groups and branches can be added to the benzene ring in the same way as we saw for the aliphatic compounds
all seem to have a sweet scent hence the name AROMATIC compounds.
Define a polyaromatic
These compounds have two or more benzene rings fused together
PAHs (polyaromatic) are serious pollutants
Primarily in soil, sediment, oil & particulate matter suspended in air
Crude oil and coal deposits contain significant amounts of PAHs
