carbon carbon bonds

Question 1

why are organometallics nucleophilic eg in methyl lithium

Answer 1

bond is polarised towards the carbon as its more electronegative, carbon develops partial negative charge (lithium has delta positive as its less electronegative)

bond polarity is determined by electronegativity of bonded atoms, electronegative atoms attract electron density in a covalent bond towards them, greater difference in electronegativity=greater degree if bond polarisation

Question 2

what are organometallics used for

Answer 2

formation of new c-c bonds

Question 3

what is formed when a ketone reacts with an organometallic

Answer 3

tertiary alcohol

Question 4

what is formed when an aldehyde reacts with an organometallic

Answer 4

secondary alcohol

Question 5

what is bond polarity

Answer 5

distribution of electrical charge between two bonded atoms

Question 6

why is carbon the site for nucleophilic attack in c=o

Answer 6

its partially positive because the oxygen is more electronegative so it pulls the electrons towards itself so the carbon is more positive

Question 7

describe the correlation between a molecules electronegativity and orbital energy

Answer 7

more electronegative the lower the energy of its orbitals

Question 8

what charges are each atom in C-Li

Answer 8

C= delta negative
Li= delta positive

Question 9

how are gringard reagents made

Answer 9

reacting magnesium turnings with alkyl halides in ether solvents, forms a solution of alkyl magnesium halide

R-X —> R-Mg-X

R=alkyl/allyl/aryl
X= I,Br,Cl

Question 10

what is oxidative insertion

Answer 10

increases oxidation state of metal, adding magnesium between alkyl and bromine bond to make a butyl magnesium bromide, Mg
(0) to Mg (ii), Mg 2 more stable so helps drive reaction

Question 11

what is THF

Answer 11

tetrahydrofuran

Question 12

describe the characteristics of ether molecules like THF and diethylether

Answer 12

aprotic, polar, dont contain any acidic hydrogen atoms in their structure

Question 13

what is Et2O

Answer 13

diethyl ether

Question 14

how are organolithium reagents synthesised

Answer 14

oxidative insertion of lithium metal and alkyl halide, each reaction requires 2 lithium atoms to make desired organolithium and a lithium halide salt

lithium oxidation state goes from lithium 0 to lithium 1

Question 15

what forms after the oxidative insertion of lithium into an alkyl halide

Answer 15

alkyllithium and a lithium halide

R-X——>R-Li + LiX
R=alkyl or aryl
X=Br, Cl
usesLi and THF

Question 16

difference between oxidative insertion of magnesium and lithium (difference between gringard and organolithium)

Answer 16

lithium requires 2 Li atoms to form alkyl lithium and lithium halide salt

Question 17

what does a basic solution mean

Answer 17

more OH- ions than H+ in solution

Question 18

why do organometallics need to be kept free from moisture

Answer 18

organometallics are extremely strong bases and they will react rapidly to produce corresponding alkane, water acts as acid and provides proton,

Question 19

what is the pKa of a C-H bond in an alkyne (triple bond cc)

Answer 19

~25, most acidic of the hydrocarbons

Question 20

name an alternative for deprotonation

Answer 20

halogen metal exchange

Question 21

why does halogen metal exchange work/how to determine which molecule gets the metal ion

Answer 21

most acidic/lower pKa (=more stable) compound will be the one with the metal compound (Li)

eg. phenyl bromide reacting with butyl lithium, butane has higher pKa than benzene so benzene is more acidic so it takes the lithium

Question 22

ways to make organometallics

Answer 22

oxidative insertion of Mg or Li into alkyl halides, deprotonation of alkynes, organ lithiation of functionalised benzene rings, halogen metal exchange, transmetallation

Question 23

how are carboxylic acids made

Answer 23

react organometallic reagent with carbon dioxide, must be under vigorously dry conditions

carbon dioxide is carbonyl containing compound and is acting as an electrophile

Question 24

what happens when carbon dioxide reacts with water

Answer 24

slowly forms carbonic acid

Question 25

chemical name for formaldehyde

Answer 25

methanal

Question 26

what can a gringard reagent and formaldehyde produce

Answer 26

primary alcohol

Question 27

how will the addition of an organometallic to a carbonyl containing compound affect the oxidation level

Answer 27

reduces it by 1

Question 28

what does addition of a organometallic to carbon dioxide produce

Answer 28

carboxylic acid

Question 29

what does addition of a organometallic to formaldehyde produce

Answer 29

primary alcohol

Question 30

what does addition of a organometallic to aldehyde produce

Answer 30

secondary alcohol

Question 31

what does addition of a organometallic to ketone produce

Answer 31

tertiary alcohol

Question 32

what does addition of a organometallic to ester produce

Answer 32

tertiary alcohol

Question 33

why do grignard reactions have to be carried out in anhydrous solvent

Answer 33

grignard reagent formed would be destroyed by its reactions with water

Question 34

is the carbon atom associated with magnesium in grignard reagent electrophilic or nucleophilic

Answer 34

nucleophilic

Question 35

is the carbon atom associated with bromine atom in bromobenzene electrophilic or nucleophilic

Answer 35

electrophilic