Organic Chemistry II

Question 1

what is a temporary dipole created

Answer 1

uneven distribution of a elections in a molecule (areas with high electron density and areas with low electron density, this occurs cause electrons are in constant motion around an atom, meaning there is an asymmetric distribution of electrons in a molecule.

Question 2

what is an induced dipole

Answer 2

temporary dipole can induce a dipole within another adjacent molecule.

Answer 3

these are the only intermolecular forces between non-polar molecules, but they exist between all molecules.

Answer 4

since they depend on movement of electrons, the more electrons molecules have, the greater the distribution forces between them; hence dispersion forces increase with increasing molar mass

Answer 5

they’re also greater for linear molecules, than branched molecules, since linear molecules allow maximum surface contact between molecules.

Question 6

what are dipole-dipole forces

Answer 6

these occur between polar molecules, due to attractive force between positive end of one molecule’s dipole, & negative end of another molecules dipole.

the larger the dipole across the molecules, the greater the forces of attraction.

Question 7

explain hydrogen bonds

Answer 7

special kind of dipole-dipole force , exists between a hydrogen bonded to either oxygen, nitrogen, fluorine, and an atom of oxygen, nitrogen or fluorine in another molecule.

this is because of the partial positive charge of the hydrogen atom is attracted to the partial negative charges on oxygen, nitrogen and fluorine, which are highly electronegative atoms.

Question 8

rank each of the following based on how strong they are , dispersion forces, dipole-dipole forces and hydrogen bonds

Answer 8

dispersion forces < dipole-dipole forces < hydrogen bonds

Question 9

what is required for melting and boiling point

Answer 9

intermolecular forces holding molecules together need to be broken, cause by the input of heat into the system, more energy is required to break strongeer intermolecular forces, hence the system must reach a higher temperature

Answer 10

it is important for solute-solvent interactions to be greater than solute-solute interactions and solvent-solvent interactions, in this way molecules of solute are able to wedge themselves between solvent molecules.

Answer 11

if this isnt the case, tis energetically unfavourable for the solute-solute interactions and the solvent-solvent interactions to be disrupted and the solute isn’t soluble in that particular solvent.

Question 12

when will subtance be solube in solvent

Answer 12

when has the same dominant intermolecular interactions

Question 13

what do organic molecules contain

Answer 13

all contain carbon backbones with hydrogen attached to avaliable carbon atoms, this is refered to as hydrocarbon skeleton,

Question 14

why are the alkanes classfied as saturated hydrocarbons

Answer 14

all carbon atoms are bonded to the maximum nubmer of hydrogen atoms

Question 15

what does straight-chained

Answer 15

where the carbon atoms form a single line, they can be branched, where internal carbon atoms are attached to extra carbon atoms, instead of hydrogen atoms.

Question 16

what does structural isomerism

Answer 16

compounds will have the same molecular formula, but different connectivityt between atoms (sequence of atoms are different)

strucutral isomers can be further borken down into chain isomers, and position isomers.

Question 17

define chain isomer

Answer 17

vary in length of the carbon backbone

Question 18

define position isomers

Answer 18

vary in the position of any attached groups

Question 19

what two forms of isomerism can alkenes exhibit

Answer 19

position isomerism and geometric isomerism

Question 20

what is position isomerism

Answer 20

the posiiton of the double-bond along the length of the carbon chain

Question 21

what is geometric isomerism

Answer 21

the arrangement of atoms around the double bond

is commonly referred to as cis/trans isomerism. arrangement f atoms around the double bond is fixed, as no rotation can occur around a double bond

Question 22

how to tel if alkene is cis or trans

Answer 22

drawing line through the axis of the double bond, then determining whether the atoms on either side of the line are the same of different. if they are the same, the alkene is cis, if they are different the alkene is trans.

seek page 21 for diagrams of cis and trans alkene geometric isomerism

Question 23

why can alkenes undergo addition reactions

Answer 23

because of their double bonds, in which their double bond is broken, and other atoms are aded to the carbon skeleton.

Question 24

how can alkene addition reactions be categorised

Answer 24

hydrogention (additon of H2)
halogenation (Br2 or Cl2)
Hydrohalogenation (HCl or HBr)
Hydration (H2O)

Answer 25

most common is halogenation

Question 26

why is halogenation involving Br2 an efficient way to determine if a substance is a alkene

Answer 26

the addition of bromine across the double bond rapidly decolourises the brown bromine water., keep in mind bromine water can also be decolourisedd by a substitution reaction with alkanes, but its slower.

Question 27

how are alkanes and alkenes similar

Answer 27

in the type of intermolecular force that exists between the molecule, as hydrocarbons are non-polar, they only experiance dispersio forces between their molecules and so have relaitvely low boiling and melting points compared to other polar organic molecuels.

Answer 28

haloalkanes and hlaoalkenes are polar, so they experuance dipole-dipole forces too, elevating the melting and boiling point,

Answer 29

alkanes are non-polar (double check this) they are generally only soluble in non-polar solvents and are sparingly soluble in polar solvents like water.

Question 30

what is an alcohol

Answer 30

hydroxyl group (-OH) replaces one of the hydrogens attached to a carbon atoms, they can be classed as primary, secondary, tertiary

Question 31

primary alcohol

Answer 31

the carbon attached to the hydroxyl group is bonded to one other carbon atoms, and two hydrogen atoms

Question 32

secondary alcohol

Answer 32

the carbon attached to the hydroxyl group is bonded to two other carbon atoms, and one hydrogen atoms

Question 33

tertriary alcohol

Answer 33

the carbon attached to the hydroxyl group is bonded to three other carbon atoms, and no hydrogen atoms

Question 34

how can alcohols be produced

Answer 34

from a hydration reaction with alkenes in which water is added across the double bond, in the presence of an acid-catalyst.

Question 35

why are alcohols polar

Answer 35

due to the hydroxyl group, the structure of the hydroxyl group allows alcohol molecules to interact predominately through hydrogen bonding, so they have higher boiling and melting points than their hydrocarbon counterparts

Question 36

solubility of alcohol

Answer 36

since they mostly interact via hydrogen bonding, alcohol are most soluble in polar solvents that also interact via hydrogen bonding, so they are readily soluble in solvents like water.

Question 37

define aldehyde

Answer 37

contain a carbonyl group (-CHO) which is bonded to a terminal carbon atom, they only ever exist at end of carbon skeleton