PH1125 - Organic Functional Groups

Question 1

what is an organic compound?

Answer 1

• any chemical compound that contains carbon

Question 2

what are carbon containing compounds that are not organic? (2)

Answer 2

• carbonates; -CO3-

- cyanide; -CN

Question 3

what is an imine?

Answer 3

• a compound with a nitrogen atom double bonded to a carbon atom

Question 4

what is an azide?

Answer 4

• a compound with -N3

Question 5

what is a functional group?

Answer 5

• specific substituents or moieties within molecules that are responsible for the characteristic chemical reactions and physical properties of those molecules

Question 6

what is the polarity and reactivity of alkanes? (4)

Answer 6

• mostly chemically unreactive
• non-polar
• not soluble in water; hydrophobic
• lipophilic

Question 7

what kind of isomers can compounds with double bonds exist as?

Answer 7

E Z isomers

Question 8

describe the reactivity of alkenes (2)

Answer 8

• reactivity due to their electron rich nature
• the pi electrons above and below the plane of the C=C double bond are more weakly held than sigma electrons and are therefore more chemically reactive

Question 9

what is regioselectivity?

Answer 9

• the preference for one orientation over another in the arrangement of a reaction product

Question 10

why do tertiary carbons have the lowest energy and the highest stability?

Answer 10

• they are stabilised by electron density from all three neighboring carbon atoms

Question 11

what is markovnikov’s rule? (2)

Answer 11

• in reactions of HX to alkenes the H bonds to the carbon with more hydrogens (fewer substituents)
• the X bonds to the carbon with more substituents (fewer hydrogens)

Question 12

what are the pharmaceutical considerations for alkenes as drugs? (4)

Answer 12

• poor water solubility
• reactive (prone to oxidation) therefore possibility of shorter shelf-life
• important in medicinal chemistry for the ability to exist as E/Z isomers
• different isomers have different biological properties

Question 13

how are alkenes reduced to alkanes? (2)

Answer 13

• hydrogen

- palladium catalyst

Question 14

what is the product when alkenes are oxidised with potassium permanganate? (2)

Answer 14

• cis-1,2-diols
• the permanganate adds across the double bond to form an unstable intermediate that reacts with water to generate the diol

Question 15

what is the alternative oxidising agent to make trans-1,2-diols? (2)

Answer 15

• peroxides

- the peroxyacid converts the alkene into an epoxide that reacts with water on the opposite side of the ring

Question 16

what does the reaction of ozone and alkenes make? (2)

Answer 16

• involves breaking the double bond

- alkenes are converted into carbonyl compounds

Question 17

what are the two principle methods for synthesizing alkenes? (2)

Answer 17

• alcohol dehydration

- wittig reaction

Question 18

what is an alkyne functional group?

Answer 18

• carbon-carbon triple bond

Question 19

what is the hybridization present in alkynes and shape?

Answer 19

• sp hybridized carbon atoms

- linear geometry; 180

Question 20

what are the physiochemical properties of alkynes? (4)

Answer 20

• rigid, non-rotatable, linear geometry where E/Z isomers are not possible
• lipophilic (non-polar) therefore with poor water solubility
• rich in pi electrons and therefore chemically reactive
• rare in nature but useful in pharmaceuticals

Question 21

how are alkynes reduced to alkanes? (3)

Answer 21

• hydrogen
• palladium catalyst
• alkyne -> alkene -> alkane

Question 22

what does the term ‘poisoning’ refer to?

Answer 22

• reduced reactivity

Question 23

what is cis-hydrogenation?

Answer 23

• both H atoms add to the same side of the double bond

Question 24

how are alkynes reduced to E-alkenes? (2)

Answer 24

• sodium

- in liquid ammonia

Question 25

what do terminal alkynes have?

Answer 25

- C≡C-H terminal H atoms which is slightly acidid

Question 26

what is the relationship between pKa and acidity?

Answer 26

- larger the pKa value the weaker the acid

Question 27

what are the physicochemical properties of haloalkanes? (3)

Answer 27

- generally chemically reactive - very useful in organic chemistry but limited use in pharmaceutics - lipophilic therefore poor water solubility

Question 28

what is a nucleophile?

Answer 28

- electron rich species than seeks an electron poor site (electron pair donor)

Question 29

as you go down the halogens in haloalkanes (fluorine to chlorine etc) does polarity increase or decrease?

Answer 29

- polarity decreases

Question 30

what is the shape and hybridisation of alcohols? (2)

Answer 30

- 109.5 tetrahedral | - sp3 hybridisation

Question 31

what makes alcohols good nucleophiles?

Answer 31

- lone pairs on the O

Question 32

why are alcohols soluble in water? (2)

Answer 32

- they are polar as oxygen is electronegative and creates a permanent dipole - this means it can form hydrogen bonds with water

Question 33

what is an alkoxide?

Answer 33

- conjugate base of an alcohol (salt formed from alcohols and strong bases)

Question 34

why cant alkoxides be used in drug molecules?

Answer 34

- they are too reactive and react readily with water to return to the parent alcohol

Question 35

how are alcohols converted to alkenes (and what kind of reaction is it)? (2)

Answer 35

- in the presence of strong acids | - water is removed and it is a dehydration reaction

Question 36

how are primary alcohols converted to aldehydes? (2)

Answer 36

- oxidisation | - manganese diodide is a mild oxidising agent

Question 37

what is an example of a strong oxidising agent?

Answer 37

- sodium/potassium dichromate (Na2Cr2O7 / K2Cr2O7)

Question 38

what is an alpha hydrogen? (2)

Answer 38

- hydrogen connected to the alpha carbon | - the alpha carbon is the carbon connected to the function group

Question 39

why can't tertiary alcohols be oxidised?

Answer 39

- they do not contain an alpha hydrogen

Question 40

what is the ether functional group?

Answer 40

- R-O-R

Question 41

are ethers polar?

Answer 41

- they are non-polar

Question 42

how are ethers synthesized? (2)

Answer 42

- primary alcohols are converted to ethers by acid-catalyzed dehydration reactions - alkoxides and alkyl halides