Chemistry - Atmospheric Elements Flashcards
What is the structure of carbon?
It has four valence electrons thus forming one to four bonds with other atoms
Alkanes
Compounds of entirely carbon/hydrogen atoms bonded by single bonds.
What is the chemical formula for an Alkane?
CnH2n+2
What are the first four alkanes?
Methane, Ethane, Propane and n-butane
How are alkanes named with side groups?
First by the longest continous chain of carbon as the base, with respective chains numbered.
What is an example of alkane nomenclature?
2,4-Dimethylhexane or 2-Bromo-3-Chloropentane
How do alkyl radicals form?
From alkanes when a H atom is replaced, remaining with an unpaired electron.
What is an example of an alkyl radical?
Methyl, Ethyl, Propyl
Why are alkyls important in the atmosphere?
The unpaired electrons make them very reactive.
Alkenes
Carbon containing compounds that have a double bond between carbons
Examples of alkenes?
Ethene, propene, 1-butene
What does the 1 in 1-butene refer to?
The carbon the double bond extends from, from the point closest to the end of the molecule with the double bond
Alkadienes
Compounds containing two-double bond like 1,3 Butadiene
Alkynes
Hydrocarbons with a single TRIPLE bond
Aromatics
Unsaturated chemical compounds with one or more planar rings of atoms joined by covalent bonds of different kinds.
Carbonyl
A functional group of a carbon bound to a hydrogen, double bonded oxygen and an R group.
What are the two types of carbonyl?
Ketone and Aldehyde
Aldehyde
This is a carbon with an R group, hydrogen atom and a double bonded oxygen.
Ketone
These are a carbon with one double-bonded oxygen and two R groups.
What is the main reaction carbonyls go?
Nucleophilic attacks
Nucleophilic Attack
This is where an electron rich species called a nucleophile, attacks an electron deficient species called an electrophile.
What do carbonyl nucleophilic attacks form?
Hydroxyl groups.
When do NA occur?
Another groups binds carbon, causing withdrawal of one of the electron pairs of the oxygen double bond, making it anioninc
Why are aledhydes more reactive?
Steric effects and Electronic effects.
Steric Effects
These are influences on a reaction course of a molecules due to occupying of space by atoms that disfavour/favour collision paths.
How do aldehydes/ketone steric effects differ?
Aldehydes exerpeinces less steric hinderance as hydrogen is smaller
How do aldehydes/ketone electrical effects differ?
Aldehydes have one less R group supplying partially postiive charge to the carbon with electrons, making the ketone carbon a weaker nucleus with less charge.
What are the sources of metahne?
Wetlands,, termites, oceans, ruminants, landfills, energy and rice.
What are methane sinks?
Soils and tropospheric OH, broken down by oxidation by hydroxyl radicals.
How does methane slow down its own decomposition?
Removal of hydroxyl, as well as hydroxyl removal by carbon monoxide removing hydroxyl from wildfires
Biogenic
Non-methane hydrocarbons of natural production like isoprene, producing ozone by photo-oxidation.
Why are biogenic hydrocarbons highly reactive?
Containing of olfinic double bonds thus shorter lifetimes.
What is isoprene released by?
Photosynthetic radiation
Nitrous Oxide(N2O)
A colurless compounds emitted by soil bacteria.
Nitrogen Dioxide(NO2)
Formed by high combustion by reaction of nitrogen in fuel and oxygen in the air.
Where is nitrogen utilised?
Nitrogen fixation
What are the two ways nitrogen is fixated?
Microorganisms conversion of N2 to ammonia/ammonium
Atmospheric conversion of N2 by cosmic radiation or lightning forming nitrogen oxide.
What are the two processes of the nitrogen cycle?
Nitrification and Denitrification
Nitrification
Conversion of ammonia to NO2 and NO3 with N2O and NO byproducts
Denitrificaiton
Conversion of soil nitrate to nitrogen gases like N2O and N2.
What is denitrifciation performed by?
Bacteria using nitrate as a terminal electron acceptor in anaerobic conditions
How much more powerful as a GHG is N2O?
300 TIMES
What are the antrhopogenic sources of N2O?
Biomass burning, agriculture and degassing of irrigation water.
What are the N2O sinks?
Stratospheric disassociation(90%) and reaction with oxygen.
