Halogenoalkanes and Hydrolysis Reactions

Question 1

what are halogenoalkanes simply

Answer 1

a homologous series of compounds

Question 2

what is the general formula of a halogenoalkane

Answer 2

CnH(2n+1)X

Question 3

what are halogenaalkanes the result of

Answer 3

replacing a hydrogen atom in a hydrocarbon with a halogen atom

Question 4

what does the X in the general formula for a halogenoalkane represent

Answer 4

a halogen

Question 5

what does the symbol R represent in organic chemistry

Answer 5

an alkyl group

Question 6

what could the formula of a halogenoalkane therefore be shortened to with that symbol

Answer 6

RX

Question 7

what would the general formula of a hydrocarbon with two or three halogen atoms bonded to it be

Answer 7

• CnH2nX2 for two

- CnH(2n-1)X3 for three

Question 8

what is the name of CH2Cl-CHCl-CH3

Answer 8

1,2-dichloropropane

Question 9

what is the name of CH2Br-CH2(CH3)-CH2Cl

Answer 9

1-bromo-3-chloro-2-methylpropane

Question 10

for 1-bromo-3-chloro-2-methylpropane, why is the bromine atom named first rather than the chlorine atom

Answer 10

because you name them in alphabetical order

Question 11

what is CH3-CH2-CH2F classified to be and why

Answer 11

• a primary halogenoalkane
• because the carbon atom the halogen atom is bonded to is only bonded to one other carbon atom itself
• meaning it is only bonded to one alkyl group

Question 12

what is CH3-CHBr-CH3 classified to be and why

Answer 12

• a secondary halogenoalkane
• because the carbon atom that the halogen atom is bonded to is bonded to two other carbon atoms itself
• meaning it is bonded to two alkyl groups

Question 13

what is (CH3)2CCl-CH2-CH3 classified to be and why

Answer 13

• a tertiary halogenoalkane
• because the carbon atom the halogen atom is bonded to is bonded to three carbon atoms itself
• meaning it is bonded to three alkyl groups

Question 14

why are most bonds in hydrocarbons non-polar

Answer 14

• because they only contain carbon and hydrogen atoms

- which have similar electronegativities

Question 15

why is the C-X bond in halogenoalkanes polar

Answer 15

because the halogen atom has a higher electronegativity than that of carbon

Question 16

what does it mean if an atom is electronegative

Answer 16

they attract electrons

Question 17

how does the electronegativity of the group 7 elements change as you go down the group

Answer 17

the electronegativity decreases

Question 18

what would the partial charges between a carbon and halogen atom be if halogen atoms are more electronegative

Answer 18

• C(sigma +)-X(sigma -)

- the carbon atom would be partially positively charged while the halogen atom would be partially negatively charged

Question 19

what would you call the carbon atom in this case

Answer 19

electron deficient

Question 20

what does the difference in the electronegativities of hydrocarbons and halogenoalkanes mean about how their level of reactivity compares

Answer 20

• halogenoalkanes are more reactive than hydrocarbons
• this is because the halogen atoms are more electronegative than them
• meaning the halogen is partially negatively charged while the carbon is more partially positively charged than it would be with a hydrogen atom
• meaning halogenoalkanes are more unstable and therefore are more reactive

Question 21

what do these carbon atoms with partially positive charges attract

Answer 21

nucleophiles

Question 22

what are nucleophiles

Answer 22

• species that are attracted to slightly positive or electron deficient parts of a molecule
• they are either negative ions or molecules with a slightly negative atom
• but always use a lone pair of electrons when attacking other species

Question 23

when a halogenoalkane is mixed with water, why does a reaction occur between the two

Answer 23

• the water molecule contains polar bonds like the halogenoalkane
• the o- oxygen atom is attracted to the o+ carbon atom of the halogenoalkane

Question 24

what is the general formula for the reaction between a halogenoalkane and water

Answer 24

• RX + H2O = ROH + HX

- or RX + H2O = ROH + H+ + X-

Question 25

what is therefore the product of the reaction between halogenoalkanes and water

Answer 25

an alcohol

Question 26

what type of reaction is this and why

Answer 26

• hydrolysis
• hydro = water and lysis = splitting
• so it is simply splitting with water