CHEM - Organic Chemistry

Question 0

What are aliphatic hydrocarbons?

Answer 0

These do not contain benzene or a benzene like structure.

Question 1

What are aromatic hydrocarbons?

Answer 1

They are hydrocarbons that contain a benzene ring or a benzene like structure. They also produce a smell.

Question 2

What bonds to alkanes contain and what is their general formula?

Answer 2

single bonds (saturated) 
CnH2n+2

Question 3

what bonds do alkenes contain and what is their structural formula?

Answer 3

at least one double bond (unsaturated)

CnH2n

Question 4

what bonds do alkynes contain and what is their structural formula?

Answer 4

triple (unsaturated)

CnH2n-2

Question 5

structural isomers

Answer 5

molecules with the same molecular formula but different structural formula.

Question 6

what happens to the melting points and boiling points of organic compounds that have the same functional group but increase in chain length

Answer 6

as chain length increases so do the melting points and boiling points
this occurs because the forces experienced increase with molar mass and require more energy to overcome

Question 7

the ability to undergo addition reactions is a chemical property of alkenes. what can it undergo these reactions with

Answer 7

alkenes undergo addition reactions with halogens such as bromine and hydrogen
-the orange/brown colour of bromine lose intensity fading towards colourless

Question 8

why do alcohols have higher boiling points than similar mass alkanes, alkenes, aldehydes and ketones

Answer 8

alcohols have higher boiling points because of their ability to undergo hydrogen bonding in addition to experiencing dispersion forces

Question 9

how can primary and secondary alcohols be distinguished from tertiary?

Answer 9

when primary and secondary alcohols are reacted with acidified potassium or sodium dichromate solution they demonstrate a colour change from orange to green as they are oxidised to aldehydes and ketones respectively.
tertiary alcohols have no hydrogen atom to be removed from the carbon and so cant be oxidised

Question 10

during fermentation heat is produced i an exothermic reaction, carbon dioxide is also observed as effervescence. what are the requirements and conditions for fermentation?

Answer 10

• simple sugar - monsaccharide (glucose)
• yeast - provide enzymes
• aqueous environment
• warm conditions - optimum 20-30 degrees C
• anaerobic conditions - limited oxygen
• slightly acidic pH

Question 11

Why is fractional distillation sometimes required in fermentation?

Answer 11

during fermentation, a maximum concentration of approximately 15% ethanol can be reached before the yeast cannot survive. Fractional distillation is therefore required to produce alcohols with a higher concentration.

Question 12

why are powdered pumice chips of glazed porcelain used in fractional distillation?

Answer 12

they are aded to avoid bumping from violent vaporisation and to instead promote smooth boiling.

Question 13

what is a fractioatiing column best used for in organic chemistry?

Answer 13

it is useful for the separation of organic materials with similar boiling points.

Question 14

what is the functional group for aldehydes and is it polar?

Answer 14

functional group: CHO, aldehyde

polar

Question 15

why do aldehydes and ketones have higher boiling poinnts than comparablee molar mass alkanes and alkenes?

Answer 15

aldehydes and ketones experience dipole dipole interactions, which are stronger than the dispersion forces in alkanes and alkenes

Question 16

how are aldehydes prepared?

Answer 16

aldehydes are prepared by the controlled oxidation of primary alcohols. a solution of acidified dichromate is added drop wise from a dropping funnel while heating (to control oxidising agent). the aldehyde boils off immediately, preventing further oxidation to a carboxylic acid.

Question 17

what is the ketone functional group and is it polar?

Answer 17

functional group: CO, ketone

polar

Question 18

how are ketones prepared?

Answer 18

ketones are prepared with the oxidation of secondary alcohols. they are heated under reflux as the oxidising agent does not need to be limited.

Question 19

what are reflux condensers used for?

Answer 19

they are used to provide extended heating in organic reactions without loss of reactants through evaporation

Question 20

how is acidified dichromate solution used to distinguish between an aldehyde and a ketone?

Answer 20

heat each with acidified potassium dichromate. with an aldehyde, orange dichromate solution turns green and with the ketone, the orange dichromate does not change colour.

Question 21

how can you distinguish between an aldehyde and a ketone by using Tollen’s reagent?

Answer 21

add Tollen’s reagent (ammonical silver nitrate) to each. the aldehyde will be oxidised to a carboxylate ion and silver ions will be reduced to form a silver deposit on the glassware.
the ketone will not be oxidised and the silver ions will not be reduced to form a silver deposit on the glassware.

Question 22

give two examples of monosaccharides

Answer 22

glucose

fructose

Question 23

give two examples of dissaccharides

Answer 23

sucrose

maltose

Question 24

give two examples of polysaccharides

Answer 24

cellulose | starch

Question 25

what is the general formula for carbohydrates and how can you best define a carbohydrate?

Answer 25

Cx(H2O)y, often x=y carbohydrates can be best defined as poly hydroxyl aldehydes or ketones or polymers of these structures

Question 26

what happens when a carbohydrate changes from the linear to the ring form?

Answer 26

in linear form, carbohydrates have either an aldehyde or ketone functional group, but these groups are not present in ring form.

Question 27

are monosaccharides soluble in polar solvents? why/why not?

Answer 27

monosaccharides are soluble in polar solvents due to the large number of hydroxyl groups compared to carbon atoms. These hydroxyl groups provide multiple opportunities for hydrogen bonding.

Question 28

why does glucose in its linear form react with acidified dichromate and Tollen's reagent but not in ring form?

Answer 28

the linear form of glucose contains the aldehyde functional group, and thus it will act as an aldehyde in the reactions with acidified dichromate and Tollen's reagent. in ring form, the functional group is lost and so glucose can not act as an aldehyde in these reactions.

Question 29

general formula for disaccharides

Answer 29

C12H22O11

Question 30

How can disaccharides be made and broken down?

Answer 30

disaccharides are formed by the condensation reaaction between two monosaccharide units with the removal of a water molecule. hydrolysis can be used to break down monosaccharides.

Question 31

are disaccharides soluble in polar solvents? why/why not ?

Answer 31

disaccharides are soluble in polar solvents due to the large number of hydroxxyl groups being able to form multiple hydrogen bonds.

Question 32

general formula for polysaccharides

Answer 32

(C6H10O5)n

Question 33

how are polysaccharides formed? and how are they broken down into disaccharides and monosaccharides?

Answer 33

polysaccharides are formed through the successive condensation of monosaccharide units with the removal of water molecules. they can be broken down into disaccharides through partial hydrolysis, and into monosaccharides with complete hydrolysis through the addition of water molecules.

Question 34

are polysaccharides soluble in polar solvents? why/why not?

Answer 34

polysaccharides are not soluble in polar solvents. they have many hydroxyl groups that are able to form hydrogen bonds with polar solvents, but due to their large molecular size, this only allows them to absorb water rather than be soluble in it

Question 35

what is the functional group for carboxylic acids and is it polar?

Answer 35

R-COOOH, carboxylic acid | polar

Question 36

how can carboxylic acids be prepared?

Answer 36

carboxylic acids can be prepared by heating primary alcohols or aldehydes with excess acidified dichromate solution.

Question 37

carboxylic acids are weak acids which partially ionnise in water? write the general equation for this

Answer 37

RCOOH + H2O -> <- RCOO- + H3O+

Question 38

acid and hydroxide neutralisation reaction

Answer 38

acid + hydroxide -> salt + water | RCOOH + OH- -> RCOO- + H2O

Question 39

Acid and carbonate neutralisation reaction

Answer 39

acid + carbonate -> salt + water + carbon dioxide | 2RCOOH + (CO3)2- -> 2RCOO- + H2O + CO2

Question 40

acid and bicarbonate neutralisation reaction

Answer 40

acid + bicarboonate -> salt + water + carbon doxide | RCOOH + HCO3- -> RCOO- + H2O + CO2

Question 41

Equation to work out pH given the H3O+ or H+ ion concentration

Answer 41

pH = -log [H+] (or H3O+) (in mol L)

Question 42

calculating H+/H3O+ ion cooncentration given pH

Answer 42

[H3O+] (in mol L) = 10^-pH

Question 43

calculatting the pH of a solution of a strong base

Answer 43

pH + pOH = 14 | [H3O+] X [OH-] = 10^-14 (at 25 degrees celsius)

Question 44

what are the boiling points of carboxylic acids in relation to comparable molar mass alkanes, alkenes, aldehydes, ketones and alcohols?

Answer 44

carboxylic acids have higher boiling points than comparable molar mass alkanes, alkenes, aldehydes, ketones and alcohols due to stronger secondary interactions (dipole dipole and hydrogen).

Question 45

why aae carboxylate ions soluble?

Answer 45

as carboxylate ions they are soluble due to the ability to form stronger ion-dipole interactions with the full negative charge formed.

Question 46

why are some drugs with carboxyl groups usually taken in the form of their salts?

Answer 46

- in ionic form these drugs are soluble in water and thus more easily administered - in tablet form these drugs are mixed as a solid form with sodium bicarbonate. when added to water a neutralisation reaction occurs to form CO2 gas (effervescence) and carboxylate ions which are now soluble due to being able to form ion-dipole interactions with their full positive charge - when in stomach, ion reacts with HCl and converts back

Question 47

what is the functional group for amines and are they polar?

Answer 47

functional group: NH2/NH/N, amine or amino | polar

Question 48

how is a protonated amine formed?

Answer 48

amines are bases. due to the un-bonded pair of electrons on the nitrogen atom, the molecules can accept one proton each from an acid. this creates a protonated amine.

Question 49

are protonated amines soluble in polar solvents?

Answer 49

yes. protonted amines offer greater solubility in polar solvents due to their ability to form ion-dipole interactions due to the fully positive charge.

Question 50

application of protonated amines

Answer 50

a large number of drugs are high molar mass amines that are insoluble in water. often these are administered as anaesthetics in a protonated form with the addition of an acid. in a protonated form they are able to form ion-dipole interactions ensuring their solubility in the aqueous environment of the human body.