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Chemistry > halo > Flashcards

halo Flashcards

1
Q

why is thionyl chloride method is preffered?

A

alkyl halide is formed with gases SO2 and HCl
the two gases are escapable and hence gives pure alkyl halide

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2
Q

allylic carbon

A

carbon is attached to a cc =

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3
Q

benzylic carbon

A

sp3 hybridised carbon which then attached to benzene ring

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4
Q

vinylic halide

A

halogen atom bonded to sp2 hybridised cc=

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5
Q

aryl halide

A

halogen atom bonded to sp2 hybridised carbon of benzene ring

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6
Q

dihalo alkane having same type of halogen atom

A

alkylidene halide or alkylene dihalides

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7
Q

when both halogen are present on the same carbon

A

geminal halide or gem- dihalide

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8
Q

halogen atom present on adjacent carbon atom

A

vicinal halides or vic - dihalides

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9
Q

what is the nature of carbon halogen bond

A

highly polar in nature because halogen atoms are electronegative and the carbon atom is electropositive.

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10
Q

how is bond length an dbond enthalpy related

A

they are inversly prop

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11
Q

as we go down the halides which high bond lenght

A

as size increases bond length increases
F< Cl< Br< I

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12
Q

how to get good yield of alkyl iodide with alcohol

A
  1. heat alcohol with Na or K I
  2. in 95% orthophosphoric acid
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13
Q

why is aryl halide not prepared with alcohols

phenolllll

A

bcz C =O bond in phenol has a partial = character and is hard to break being stronger than single bond

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13
Q

why is preparation of haloalkanes with free radical halogenation not preffered

A

the products are mixture of isomeric mono- and polyhaloalkanes which is difficult to separate an dhence the yield is low

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14
Q

how do u detect the presence of a = in a molecule

A

when u add bromine inCCl4 to an alkeneit results in discharge of reddish brown of bromine
the addition results in synthesis of vic- dibromide, which is colourless

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15
Q

what happens to the reaction with the help of NaCl or NaBr precipitate in FINKELSTEIN rnx

A

the precipitate in dry acetone faciliate the forward reacrtion a/c to LE CHatelier principle

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16
Q

RINXELSTE I Na in dry area

halogen exchange

A

R- X + Na I-> R-I + NaX

X = cl, br

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17
Q

( SbWAgF3TS RNX Br )FI🔥🔥

A

R - Br + Ag F-> R F + AgBr

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18
Q

all the metallic fluorides used in SWARTS REACN

A

AgF
SbF3
CoF2
Hg2F2

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19
Q

SANDMEYERS RNX

A

⌬N2+X- -cu2X2/ HX-> ⌬x +N2

x = CL,BR

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20
Q

FLUORO compoundas not prepared by electrophilic subs of HC

A

DUE TO HIGH REACTIVITY

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21
Q

RNX OF I ARE reversible in nature and require oxi agent to oxidise HI during iodination
true or false

A

true

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22
Q

how do u separate ortho and para isomers of halotoulene

A

separated by their difference in melting p

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23
Q

Why is sulphuric acid not used during the reaction of alcohols with KI?

A

H2SO4 is a strong oxidising agent and it oxidises HI formed during the reaction to I2 which does not react with alcohol.

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24
Q

why is boiling points of halogen derivatives considerably higher than HYDROCARBONS

A

Due to strong intermolecular force of attraction (dipole–dipole and van der Waals forces)​, large amount​ of heat is required to break strong intermolecular forces, so boiling point increases.

25
Q

For the same alkyl group, the boiling point of alkyl halides decrease in the order:

ATTRACTION IS STRONGER AS MOLECULES GET BIGGER IN SIZE AND HAVE MORE e-

A

RI> RBr> RCl> RF

This is because as the size of halogen increases, the magnitude of van der Waals forces increase, and hence the boiling point increase.

26
Q

how is B.P affected with increase in branching

A

B.P decreases

27
Q

account:
the B.P of dihalobenzenes are nearly same but their para isomer have higher M.P than ortho or meta isomers

A

due to its symmetry that fits in the crystal lattice better compared to o and m isomers

28
Q

what all factors increase the density of halocompounds

A
  1. c atoms increase
  2. increase in halogen atoms
  3. atomic mass of halogen atom I> Br> Cl
29
Q

the rnx in which a nu replace an already existing nu is called

A

NUCLEOPHILIC SUBTI RNX

29
Q

what are substrate in NUCLEOPHILIC SUBTI RNX

A

HALO ALKANES

30
Q

AMBIDENT NU
WITH example

A

cyanides and nitrites posses 2 nucleophilic centres

31
Q

why Ag CN gives main product as isocyanides

A

Ag CN is mainly covalent in nature and nitrogen is free to donate e- pair forming isocyanide as main product
while KCN is ionic an dprovides Cyanide ions. and the attack take place thru C atom and not nitrogen as C-C bond is more stable than C-N bond

less electronegativity difference

32
Q

Sn2

A

order- 2
one step process
inversion of configuration
no intermediate formed
depends on conc of both reactants
in aprotic solvents
reactivity: methyl> 1o> 2o> 3o (steric effect)
reactivity of halide: RI > R-Br> RCl> RF

33
Q

SN1
substitution nuclephilic unimolecular

A

1st order rnx
rate depence on only one reactant
rnx take place in polar protic solvent
2 step process
1. formation of C+ (slowest and reversible)
2. nucleophilic attack

racemisation
depends on stability of C+ : 3o> 2o>1o
reactivity of halide: RI > R-Br> RCl> RF

34
Q

allylic and benzylic halides are highly reactive toward SN1 due to

A

This is because they form stable carbocation due to resonance

35
Q

assymetric or stereocentre

A

carbon with all the substituents attached to it are different

it cant be superimposed

36
Q

enantiomer

A

the stereoisomers related to each other as non superimposable mirror images

37
Q

racemic mixture

A

a mixture havig 2 enentiomers in equal prop will have zero optical rotation, as rotation of one will cancel out the rotation of other isomer. such mixture is called racemic mixture

38
Q

racemisation

A

the process of conversion of enetiomers into racemic mixture is

39
Q

retention

A

if during a rnx no bond is broken of the stereocentre then the product will hav eth esma general config
the rnx proceed with retention of config

40
Q

B elimination major product is

dehydrohalogenation

A

zaistev rule
greater no. of alkyl grp attached to =ly bonded c atom

41
Q

WURTZ RNX

A

RX + Na
RX + Na= dry ether
RR + 2NaX

42
Q

4 reasons why aryl halides are less reactive towards nucleophilic substitution rnx

A
  1. resonance effect
    * e- pair on X atom are in conjugation with π e- of the ring
    * c- x bond acquires a partial = character due to resonance which is harder to break
  2. difference in hybridisation of C-X bond
    * sp2 hybridised c of the ring has more s character
    * so it’s more electronegative
    * can hold e- pair of c- x bond more tughtly
    * so bond length decrease
    * and it is harder to break a shorter bond
  3. instability of phenyl cation
    * the phenyl cation formed by self ionisation will not be stable by resonance
    * SN1 IS RULED OUT
  4. due to possible repulsion
    * HIFHLY unlikely for a e- rich nucleophile to approach an e- rich arene
43
Q

chlorobenzene can be converterted to phenyl by

A
  1. NaOH. 623 K, 300atm
  2. H+
44
Q

Chloro4-nitrobenzene is converted to 4- nitrophenyl by

the presence of EWG at o and p increases reactivity of haloarenes

A
  1. NaOH, 443K
  2. H+
45
Q

why NO2 group show its affect only at o and p not meta position

A
  • The presence of nitro group at ortho- and para-positions withdraws the electron density from the benzene ring and thus facilitates the attack of the nucleophile on haloarene.
  • The carbanion thus formed is stabilised through resonance.
  • The negative charge appears at ortho- and para- positions with respect to the halogen substituent is stabilised by –NO2 group
  • while in case of metanitrobenzene, none of the resonating structures bear the negative charge on carbon atom bearing the –NO2 group.
  • Therefore, the presence of nitro group at metaposition does not stabilise the negative charge and no effect on reactivity is observed by the presence of –NO2 group at meta-position
46
Q

halogen is slightly deactivating is ortho para directing
true or false

A

true

47
Q

although chlorine is EWG yet it is *o and p * directing in ESR why

A
  1. chlorine withdraws e- thru Ieff and release e- thru R
  2. thru R, X tends to stabilise C+ and eff is more pronounce at o and p posts
  3. the I eff is >str R and cause net e- withdrawal and thus cos net deactivation
  4. R eff tends to oppose the I eff for the attack at o and p post and hence make the deactivation lessfor o and p post

reactivity controled- stronger I effect
orient controled - R eff

47
Q

why halogen is deactivating the ring

A

**they withdraw electrons through inductive effect ** more strongly than they donate electrons through resonance effect.

48
Q

WURTZ FITTIG RNX

A

⌬-X +Na +R-x -dry ether> ⌬-R +NaX

49
Q

FITTIG RNX 🕶

A

2⌬-x +2Na -dry ether-> ⌬-⌬ +2NaX

50
Q

poly halogen compound?

A

carbon aompounds containinig more than oneX compounds

51
Q

CH2Cl2
dichloro methane
methyylenechloride
🖌🧪💊🗜😵🥴😶😡🤩👁

A
  1. used: solvent in paint remover. propellant in aerosal an dprocess solvent in drugs. metal cleaning and finishing solvent ,
  2. harms human CNS, low levels - impaired hearing and vision
    high level- dizzy, nausea, tingling an dnu,bess of toe and finger
    direct skin- burning and mild redness
    direct eye- burn cornea
52
Q

CHCl3
Chloroform
trichloromethane
💪💊I 👩‍⚕️🧊😵🥱🤕🧠👦🦿

A
  • solvent for fats, alkaloids and iodine
  • used as anaesthertic now less toxic ether
  • used majorly freon refrigersnt R-22
  • 900ppm - depresses CNs - dizzy, fatigue and headache
  • chronic chloroform exposure dmage liver( where it metabolise into phosgene) and kidney
  • sore when skin is immersed in chcl3
53
Q

why chloroform kept in dark bottles

A

Chloroform is slowly oxidised by air in the presence of light to an extremely poisonous gas phosgene. Thus it is stored in closed dark coloured bottles completely filled so that air is kept out.
2CHCl3(Chloroform)+O2 Sunlight−−−−−→2HCl+2COCl2(Phosgene)

54
Q

triiodomethane
iodoform
chI3

A

earlier used as antiseptic due to liberation of free iodine and not due to iodoform itself

replaced due to its smell

55
Q

CCl4
🧊🚁👨‍⚕️🧼🧽🧯🧠👁🤪🥴🤮🏴‍☠️🖤

A
  • refrigerant. propellant. feedstock for CFCs. pharmaceutical manufacturinfg and general solovent
  • cleaning fluid as degreasing agen, spot remover an dfire extinguiser
  • liver cancer - may be
  • common effect- d, light headed, nausea, vomit
  • high effect = stupor, coma, and death
  • heart beat stop and irritate eye
56
Q

freons

A

CFC of methan and ethane collectively
* extremely stable, non toxic, non corrosive esily liguifib;r gases
* freon 12 - manu from tetrachloromethane by SWARTS RNX
* areosal propellant, refrigenrt and air conditiong

57
Q

ddt🦟💀🐟

A

1st chlorinated insecticde

dichlorodiphenyltrichloroethane

58
Q

convert

(ii) Ethane to bromoethene

A
  1. bromination
  2. b elmination
  3. vic halide test
  4. b elimination

Chemistry (9 decks)

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