Organic chemistry

Question 1

Define molecular formula

Answer 1

expresses the exact composition of a molecule or substance

Question 2

define empirical formula

Answer 2

the simplest whole number ratio of atoms of each element in a compound

Question 3

define heteroatom

Answer 3

any atom which is not carbon or hydrogen

Question 4

define constitutioanl isomers

Answer 4

they vary in structure through their arrangement of atoms

Question 5

what is the difference between the labels isopropyl and propyl

Answer 5

isopropyl is when the bond from the main carbon chain is connected to the middle carbon on the propyl chain, rather than the first

Question 6

how do you name an ether

Answer 6

identify the shortest chain, put oxy on the end, end the word with the longest chain

Question 7

what is the difference between an ether and an ester

Answer 7

an ether has an oxygen atom in the chain of carbons, but an ester has an oxygen in the chain, and the next carbon is connected to an oxygen via a double bond

Question 8

define polar covalent bond

Answer 8

when two atoms are bonded covalently but they have significantly different electronegativities and so the more electronegative atom finds the pair of electrons closer to it

Question 9

define electronegativity

Answer 9

the tendency of an atom to attract a shared pair of electrons towards itself

Question 10

list all of the types of bonds from strongest to weakest

Answer 10

covalent, ionic, metallic, hydrogen, dipole-dipole, london dispersion

Question 11

why do longer alkanes have a higher melting/boiling point than shorter ones

Answer 11

the longer the chain, the more attractive forces per molecule, meaning more energy is required to break the intermolecular forces

Question 12

why do alkanes float on water

Answer 12

they are less dense, non-polar, and hydrophobic

Question 13

what do alkanes form in their solid state

Answer 13

a wax

Question 14

why do branched alkanes have lower melting and boiling points then their linear isomers

Answer 14

they have substituted chains which are not able to pack as efficiently

Question 15

define conformations

Answer 15

the different arrangements of atoms in a molecule in space due to rotation

Question 16

do eclipsed or staggered newman projections have higher energy

Answer 16

eclipsed as lower distance between the eclipsing atoms

Question 17

what are the three types of ring strain

Answer 17

angle - angles deviate from 109
torsional - methyl groups on adjacent carbons eclipsed
steric - methyl on non-adjacent carbons are too close

Question 18

define axial bonds

Answer 18

the six axial bonds, one on each carbon in a ring, are parallel and alternate up and down

Question 19

define equatorial bonds

Answer 19

the six equatorial bonds, one on each carbon in a ring, come in three sets of two parallel lines, they also alternate between sides around the ring

Question 20

are axial or equatorial bonds higher in energy

Answer 20

axial

Question 21

why are carbon-carbon sigma bonds stronger than carbon-carbon pi bonds

Answer 21

they are less susceptible to electrons

Question 22

why are there more trans isomers than cis

Answer 22

they are thermodynamically more stable due to steric strain existing in the cis form

Question 23

what is the difference between E and Z isomers

Answer 23

E - higher ranked groups are on opposite sides
Z - higher ranked groups are on the same side

Question 24

define stereoisomers

Answer 24

same atomic connectivity but differ in special arrangement of the constituent atoms

Question 25

define enantiomers (optical isomers)

Answer 25

non-superimposable mirror images of each other, and are said to be chiral

Question 26

define optically active

Answer 26

it rotates plane polarised light

Question 27

define diastereoisomers

Answer 27

either member of a pair of substances that differ with respect to the configurations of their molecules

Question 28

name the four types of organic reactions

Answer 28

addition, elimination, substitution, rearrangement

Question 29

what are the two types of bond formation

Answer 29

homolytic (symmetrical) and heterolytic (unsymmetrical)

Question 30

define concerted reaction

Answer 30

a chemical reaction in which all bond breaking and making occurs in a single step

Question 31

define electrophile

Answer 31

electron pair acceptor

Question 32

define nucleophile

Answer 32

electron pair donator

Question 33

describe the reaction of hydrochloric acid with ethene

Answer 33

the alkene behaves as a nucleophile and the proton from HCl behaves as an electrophile. The pi bond on the alkene breaks and the two electrons form a new bond with the proton. A carbocation is formed, which then behaves as an electrophile for the Cl-, forming a bond