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organic chem and analysis Flashcards

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1
Q

why was kekules model incorrect

A

benzene doesn’t decolourise bromine water
has a much less exothermic enthalpy change of hydrogenation than expected

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2
Q

what are the conditions for nitration of benzene?

A

50ºC
concentrated acids
conc H2SO4 catalyst

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3
Q

what are examples of a halogen carrier catalyst?

A

AlCl3
FeCl3
AlBr3
FeBr3

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4
Q

What are examples of election donating groups?

A

OH
NH2
CH3

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5
Q

What do election donating groups do?

A

Donate electron density into the pi system
Make it more reactive
Activate electrophile attack
Direct incoming electrophile to Carbon 2 and 4

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6
Q

What is an example of an electron withdrawing group?

A

NO2

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7
Q

What do election withdrawing groups do?

A

Remove electron density from the pi system
Make it less reactive
Deactivate electrophile attack
Direct incoming electrophiles to carbon 3

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8
Q

What is carbon position 2/6 called

A

Ortho

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9
Q

What is carbon position 3/5 called

A

Meta

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10
Q

What is carbon position 4 called?

A

Para

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11
Q

what are examples of stationary phase in TLC?

A

silica
alumina

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12
Q

What is the stationary phase in gas chromatography?

A

Long coiled column, usually a non volatile liquid

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13
Q

What is the mobile phase in gas chromatography?

A

Inert carrier gas
Eg helium, nitrogen

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14
Q

what is the test for alkenes?

A

shake w orange bromine water
addition reaction takes place
decolourises bromine water

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15
Q

what is the test for haloalkanes?

A

warm the haloalkane with NaOH in a mixture of ethanol and water
haloalkane will undergo nucleophilic substitution and release the halide ion into solution

acidify sample of halide ion w dilute nitric acid to remove carbonate ions
add silver nitrate
forms silver halide ppt

AgCl - white
AgBr - cream
AgI - yellow

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16
Q

what is the test for carbonyls?

A

pale orange solution of 2,4-DNP dissolved in methanol then H2SO4
add few drops of carbonyl to 5cm3 of 2,4-DNP and leave to stand
add few drops of H2SO4
yellow/ orange ppt forms

17
Q

what is the test for aldehydes?

A

warm tollens reagent (aqueous alkaline solution of silver nitrate in excess ammonia solution) w an aldehyde
aldehyde oxidised to a carboxylic acid and Ag+ reduced to Ag atoms
in the alkeline conditions, the carboxylic acid will become a carboxylate ion and form a salt
Ag atoms dorm a silver mirror on inside of test tube
ketones cannot be oxidised so give neg test
OR
turn blue fehlings solution to orange/ brick red ppt

18
Q

what is the test for alcohols?

A

1cm3 of alcohol in test tube
1cm3 of acidified potassium dichromate (oxidising agent)
add stopper to test tube and shake
place in 60ºC water bath for few mins
primary/ secondary= orange to green
tertiary= stays orange

19
Q

what is the test for carboxylic acids?

A

pH probe or dip end of glass rod in solution then on indicator paper- pH3
OR
1-2cm3 sodium carbonate added
gas bubbled produced
gas bulbbled into limewater
limewater turns cloudy
confirming gas is CO2

20
Q

what is the test for phenols?

A

shaken w bromine water
substitution reaction
decolourises bromine water
white ppt forms

21
Q

what are samples measured against in NMR and why?

A

TMS
produces single intense peak at far rhs
protons highly shielded
inert
non toxic

22
Q

what are the components of a NMR spectrometer?

A

radio wave source
radio wave detector
stable magnetic field formed by superconducting coils and elecrtomagnets

23
Q

which type of atoms need more energy to resonate in NMR?

A

more deshielded

24
Q

what are samples for NMR analysis dissolved in and why is this used?

A

deuterated solvents
all 1H replaced by deuterium D 2H
produces no signals in NMR

25
Q

in proton NMR, what does the ratio of the relevant areas under each peak represent?

A

ratio of how many protons responsible for each peak

26
Q

in proton NMR, how is the number of adjacent protons represented?

A

number of adjacent protons + 1
= number of sub peaks

chem (4 decks)

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