Module 4 Section 2 Flashcards
What is a primary alcohol?
When the OH is attached to a carbon which is only attached to one other alkyl group
What is a secondary alcohol?
When the OH is attached to a carbon with 2 alkyl groups attached
What is a tertiary alcohol?
When the OH is attached to a carbon atom with 3 alkyl groups attached to it
What happens to the solubility of alcohols in water as you get bigger molecules (ie methanol compared to butanol or something) and why?
Smaller molecules are more soluble than bigger molecules
Smaller molecules are more polar so they form hydrogen bonds more easily than bigger molecules.
With bigger molecules, most of the molecule is a non-polar carbon chain, so there’s less attraction to H2O molecules
What property does hydrogen bonding between alcohols give them?
Low volatility (don’t evaporate easily)
Alcohols can form hydrogen bonds with each other
What is the difference between an aldehyde and a ketone?
They both have the same functional group (c=o)
The difference is that the carbonyl carbon atom is attached to ONE alkyl group for an ALDEHYDE
Whereas with a KETONE it is attached to TWO alkyl groups
Look up oxidation of alcohols stuff
Textbook
What is a nucleophile?
An electron pair donor
Could be a negative ion it an atom with a lone pair of electrons
Why can haloalkanes react with nucleophiles?
The carbon-halogen bond in a haloalkane is polar
So it can be attacked by a nucleophile
What mechanism causes haloalkanes to react to make alcohols?
Nucleophilic substitution
Nucleophile attacks polar carbon-halogen bond
Leaves the halogen on its own (negatively charged) and an alcohol
What dictates how fast a haloalkane can be hydrolysed (made into an alcohol)
The bond enthalpy of the carbon-halogen bond
The bond enthalpy decreases down the halogen group, so an iodoalkane would react the fastest
(As the electronegativity decreases down the group)
What are the useful features of CFC’s (chlorofluorocarbons)?
Stable - strong carbon halogen bonds
Volatile
Non flammable
Non toxic
What’s the problem with CFC’s?
They destroy ozone, the protective layer of the earth from harmful radiation
Ozone has formula O3
What is the equation for the formation of ozone?
O2 -> O + O
O2 + O -> O3
The first reaction is caused by UV light, which makes two oxygen free radicals
These then attack other oxygen molecules to make ozone
How do CFC’s destroy ozone?
UV light causes chlorine free radicals to be formed
These then react with ozone to form a ClO radical and an oxygen molecule.
Free radical substitution takes place
What are the equations involved in the 3 steps of free radical substitution of ozone with CFC’s
Initiation:
CF2Cl2 -> .CF2Cl + Cl.
.= free radical -Happens under UV light
Propagation:
Cl. +O3 -> O2 + ClO.
ClO. + O -> O2 + Cl.
Termination:
Just combine some free radicals from the previous reactions into one normal compound
What does it mean when something is anthropogenic?
Caused by humans
How does Infrared Spectroscopy work?
IR radiation passes through a sample
Absorbed by covalent bonds in the molecules, causing them to vibrate more
Different bonds absorb different frequencies, so you can tell what bonds are present in a compound based on it
What does it look like when a OH group from a carboxylic acid is present in a IR spec?
A broad peak around 2500-3300
Normally merges with the CH peak so you get this wide peak
What does an IR spec look like when a C=O bond is present?
Peak around 1700, looks like a sword
Present in aldehydes, ketones, carboxylic acids, esters
What does an IR spec look like when OH (alcohol) is present
Peak around 3200-3600
Past the CH peak
Why are some organic reactions conducted under reflux?
Organic substances are usually flammable and volatile (low boiling points)
Means they’re gonna evaporate before they have time to react
Doing it under reflux means they’re constantly being boiled, evaporated and condensed, giving them time to react.
When is an organic reaction performed under distillation?
When the reactants and products have very different boiling points
Substances will evaporate out of the mixture in order of increasing boiling point
Eg if the product has a lower BP than starting materials, the reaction mixture can be heated so that the product leaves the mixture and travels out of the distillation apparatus and can be collected
How do you purify a volatile liquid?
If the impurities and product have different BP’s, you’d put it in the distillation apparatus
Use the BP’s to separate the impurities and the product
How do you separate soluble impurities from an insoluble product?
Use a separation funnel
Put product in, funnel is shaken then allowed to settle. This causes the organic layer to sit on top of the aqueous layer (it’s less dense)
You then open the stopper and let the aqueous layer out
What is the charge on all ions that are detected by a mass spectrometer
+1
What does m/z refer to
Mass-to-charge ratio
How can the molecular mass of a substance e determined from a mass spectrometer
The m/z value of the furthest peak on a mass spectrum
What are all the other peaks in a mass spectrum showing
These peaks represent fragments that can be made from breaking down the original molecule into smaller chains
What type of molecular fragments are not detected by the mass spectrometer
Uncharged radicals
How do you purify an organic product?
By using a separating funnel
Add water so that you can identify the organic layer
Invert to mix the contents, then allow the layers to settle
Release the aqueous layer
Then release the organic
What is a ‘drying agent’
A drying agent is an anhydrous inorganic salt that will readily take up water to become hydrated
How would you dry an organic product that may have some water left in it?
By using a drying agent
Add it to the organic liquid and put a stopper on the flask. Swirl it
Add drying agent until some of it is dispersed in the solution as a fine powder
Decant the liquid from the solid into another flask. It should be clear if it’s dry
