organic chemystery

Question 1

what is tautomerization?

Answer 1

POOP

interconversion of 2 isomers by simultaneous shift of proton and double bond. (moving electron cloud?)

Question 2

what type of hybridisation is apparent in methane?

Answer 2

sp3 hybridisation (4 bonds surrounding it so s, sp,sp2,sp3)

Question 3

which has the greatest polar bond?

Answer 3

C-F The bond gets increasingly polar as a more electronegative atom is attached to the carbon. Fluorine is the most electronegative element attached to the carbon here.

Question 4

Secondary carbons are how many times more reactive than primary carbons?

Answer 4

Secondary carbons are x4 as reactive as primary carbons. Tertiary carbons are x5 as reactive as primary carbons. So radioactivity ratio is 1:4:5

tertiary radical more stable but more reactive

Question 5

which of the following reactions requires a fine nickel catalyst?
A elimination
B halogenation
C hydrohalogenation
D hydration
E hydrogenation

Answer 5

hydrogenation reactions (addition of H2 to an alkene = alkane) requires a stong calalyst like Nickel catalyst !

Question 6

In what group is the Sn1 nucleophilic substitution reaction most likely to occur?

Answer 6

tertiary (and secondary) carbons. compounds that can form a stable carbocation react by the SN1 mechanism

Question 7

what type of hybridisation is apparent in ethene?

Answer 7

sp2 (there are 4 bonds but one of them is a double bond so techincally 3 bonds so we do s,sp,sp2)

Question 8

Which of the following compounds will cause a silver mirror to develop during the chemical test using Tollen's Reagent (Ag(NH3)2+)?
A Aldehydes only
B Ketones only
C Aldehydes and ketones
D Aldehydes and alpha hydroxy ketones
E Carboxylic acids

Answer 8

Aldehydes and alpha hydroxy ketones. alpha hydroxy ketones have an -OH group on the carbon next to the carbonyl group which makes the compound more reducing and so able to reduce the reagent to liberate the silver atoms which form the mirror.

Reducing carbohydrates

Question 9

which amino acid is not present as an enantiomer?
A serine 
B alanine
C glycine 
D cysteine
E histidine

Answer 9

glycine: glycine cannot act as a stereoisomer as it has 2 identical atoms (2 H atoms) attached to the central carbon atom

Question 10

in hyperconjugation reaction what type of hybridisation does the carbon centre change into?

Answer 10

sp3to sp2 . Radicals are stabilised by hyperconjugation.

Delocalisation of the bonding electrons from carbon next door by overlap with partly filled p orbital. Theres a net stabilising effect (less energy required to generate the radicals)

Question 11

What is theMichaelis-Menten equation?

Answer 11

v = Vmax([S]/Km+[S])

Question 12

C1-? alcohols are soluble in water before the long chain predominates and makes them insoluble?

Answer 12

C1-C3 alcohols are soluble in water.
As the chain length increases, solubility decreases, as the HYDROPHOBIC tail dominates and have higher boling points than alkanes

> > this is the same for COOH except its up to C4

Question 13

what is the Baeyer test used to test for in organic chemistry?

Answer 13

test prescence of a double bond e.g alkene

a postive test is when the KMnO4 is used to oxidise the double bond and the purple colour disappears

Question 14

What is the empirical formula for carbohydrates?

Answer 14

Cn(H2O)n

Question 15

what is valence shell electron configuration of carbon?

Answer 15

1s2 2s2 2p2

Question 16

What is the difference between homolytic and heterolytic bond cleavage?

Answer 16

Homolytic bond cleavage is when one electron is transferred resulting in the formation of radicals

Heterolytic bond cleavage is when 2 electrons are transferred resulting in formation of ions

Question 17

is ethanal (acetal-aldehyde) chiral or achiral?
CH3-C=O
\
H

Answer 17

this is achiral as it onoly has 3 groups NOT 4!

Question 18

if the highest priority (highest atomic number) groups are on the same side is it..
E- isomer
Z- isomer

Answer 18

Z - isomer
> on zee zame zide
The atom which has the higher atomic number is given the higher priority.

Question 19

why is teritary carbocation more stable?

Answer 19

The tertiary carbocation is the most stable as it has 3 bonding pairs which each have electron clouds that can stabilise it.

Question 20

When added together, an alcohol and carboxylic acid (ester) will not spontaneously react. What kind of catalyst is required for esterification?
A An inorganic acid catalyst, such as concentrated sulphuric acid.
B A strong basic catalyst, such as sodium hydroxide.
C A nickel catalyst.
D A nitrogen (II) oxide catalyst.
E A platinum catalyst.

Answer 20

OPTION

inorganic ACID is required to make the alcohol and the carboxylic acid react.
catalyst protonates the carbon allows resosnance, attack by alchol and removal of WATER (hydrolysis reaction)

Question 21

How is ammonium sulphate used to separate proteins in purification?
A By using charged molecules to separate the mixture into fractions.
B By using the size of the molecules to separate the mixture into fractions.
C By acting as a binding partner to exploit the affinity of the target protein.
D By outcompeting the protein so that the protein precipitates out.

Answer 21

The ammonium sulphate is more soluble in water than the protein, so outcompetes the protein for water availability. Highly polar proteins require more salt to be added in order to precipitate out.

Question 22

which acid is stornger?

propanoic acid or octanoic acid?

Answer 22

proponic acid stronger as it has the shorter carbon chain so more likley to give up the proton

as carbon chain gets longer, its more reactive and negative so tends to act more basic = weaker acid

Question 23

Which of these contains a triple carbon bond?
A Alkane
B Alkene
C Alkyne
D Alkanols
E No hydrocarbons contain triple bonds

Answer 23

OPTION C

A - alkanes contain single bonds
B - alkenes contain double bonds
C - alkynes contain triple bonds
D - alkanols contain -OH group 
E - false

Question 24

Why are ethers often used as solvents?
They are very polar.
They are very reactive. 
They are not very polar. 
They are not very reactive. 
They can form extensive hydrogen bonds between molecules.

Answer 24

OPTION D

Ethers also more polar than alkanes (due to Oxygen), but less polar than alcohols, and
Ethers can form hydrogen bonds with water they can’t form between other ether molecules.
Shorter they are = lower the boiling point

Question 25

Why are tertiary carbons 5x as reactive as primary carbons?

Answer 25

DUE TO HYPERCONJUGATION
Hyperconjugation stabilises radicals - tertiary carbons have 3 bonding pairs stabilising a lone electron, whereas primary carbons only have 1

Question 26

Which of these statements is true?
A Alkenes do not contain a pi bond, but alkanes do
B When naming alkenes, the end with the closest branch takes precedent over the double bond
C The I-Z system is used to assign groups priorities in alkenes
D Alkenes can have many constitutional isomers
E Cumulated double bonds in alkenes occur in patterns of double, single, double etc.

Answer 26

OPTION D is true as the structural arrangement of alkene double bond can be anywhere!

A - alkenes do contain pi bonds double bond), alkanes do not
b- double bond takes precedent in naming alkenes
c- it’s the E-Z system, NOT I-Z haha
E - conjugated double bonds have pattern of double, single, double etc. and cumulated double bonds are side by side

Question 27

6 carbon aldose sugars have 4 chiral centres. How many stereoisomers are possible?

Answer 27

16 (2 to the power of 4!

Question 28

CH3-O-CH2CH name this please

Answer 28

methoxyethane. Meth = 2 ethane =C2H6 oxy=oxygen

this is an ETHER - oxygen connects 2 alkyl groups

Question 29

what is the difference between sigma and pi bonds

Answer 29

sigma - end to end overlap of orbital
pi - side to side interaction (as seen in DOUBLE BONDS made of one pi and one sigma bond) creating electron clouds

>

Question 30

what are the properties of carbon

Answer 30

electrongetsvit of 2.5
has 4 valence electrons
can form covalent (with itself) or polar covalent bonds (with other elements)

Question 31

how does a branched lakne compae to a straight alkane in terms of S.A

Answer 31

branched has a smaller s.a so can’t pack well and therer are fewer intermoleular forces

Question 32

in conformational isomers, which is low energy
A in eclipsed state
B in staggered state

Answer 32

> conformational isomers are rotations around a single bond
staggered low energy
eclipsed is high energy

Question 33

what is the main difference between an alkane and a haloalkane

Answer 33

alkanes aren’t polar as hydrogen and carbon have similar electronegtivities whilst haloalkanes are POLAR

Question 34

how cna you describe an enantomer

Answer 34

R+S system uses rotation and priority nubers to describe chiral structure

if from low to high priority it is clockwise its R enantimoer

Question 35

why can alkenes act as nucleophiles

Answer 35

alkenes have large electron clouds so are electron rich areas capable of donating electron pairs

it can induce dipoles in halogen (cl-cl , Br-b=Br) during halogenation

Question 36

what are the properties of ethers?

Answer 36

more polar than alkanes due to oxygen
less polar than alcohol as it lacks the OH

shorter = lower boil point
unreactive so good solvents
can hydrogen bond to water

Question 37

benzen can do elecrophilci substitutiion but never elctrophilic addition. why?

Answer 37

this woudl break the stable ring strucutre of benzene