Organic chem wace

Question 1

What defines homologous series

Answer 1

-similar structure
-similar chemical properties
-same general formula
-pattern to their physical properties

Question 2

Define an alkane. Formula? Saturation?

Answer 2

Hydrocarbon containing only single bonds. All carbon-carbon are covalent, single bonds.
- CnH2n+2
-saturated

Question 3

Define structural isomers

Answer 3

same molecular formula but different structural formula

Question 4

Describe the melting/boiling point of alkanes.
What occurs to BP with straight chains in contrast to branched

Answer 4

-increase with more carbon atoms in formula (increase length)
-increase atoms=greater intermolecular (dispersion) forces
-greater intermolecular forces=increased energy to separate molecules
-increased energy required=increased BP

Straight have increased interaction than branched. Greater branching=decreased BP

Question 5

Describe the solubility of alkanes

Answer 5

Nonpolar. Immiscible in water
Soluble in most organic solvents (like dissolves like)

Question 6

Define an alkene. Formula? Saturation?

Answer 6

Contain a double bond
-CnH2n
-unsaturated therefore addition can occur
-both structural and geometric isomers

Question 7

Describe the structural and geometric isomers of alkenes

Answer 7

Structural
Differentiate in bond positioning, branching

Geometric
Stereoisomerism occurs due to restricted rotation of double bond
Cis: same side atom
Trans: different side atom

Question 8

Define an isomer

Answer 8

Different physical but same chemical properties due to similar molecular masses

Question 9

Describe the melting/boiling point of alkenes.
Solubility?

Answer 9

BP increases at increase in carbon atoms in formula
Greater branching = lower BP

Solubility: miscible in organic

Question 10

Describe alcohol as a functional group

Answer 10

• Has an OH group attached to C atom
• can classify as primary, secondary, or tertiary according to position of OH on carbon skeleton
  -Name suffix (ol) or prefix (hydroxy)

Question 11

Describe aldehyde as a functional group

Answer 11

• Has C=O group at end of carbon chain
  -polar molecules
  -Name suffix (al)

Question 12

Describe ketone as a functional group

Answer 12

• Has a C=O group next door to 2 carbons
  -polar molecules
  -name suffix one
  -number may be used before -one to indicate first carbon involved

Question 13

Describe carboxylic acid as a functional group

Answer 13

-Has OH and C=O groups at same carbom atom
-this COOH group must be at end of chain
-can form H bonds between molecules
-name suffix (oic acid)

Question 14

Describe ester as a functional group

Answer 14

-one oxygen is part of C=O bond, other is next door, sandwiched between 2 carbons
-made by reacting alcohol with carboxylic acid
-name suffixs yl (first) and oate (second)

Question 15

Describe amine as a functional group

Answer 15

-has an NH2 group attached to carbon chain
-name suffix (amine) prefix (amino)

Question 16

Describe amide as a functional group

Answer 16

-has NH2 group and C=O bond
-both functional groups are on same carbon
-name suffix (amide)

Question 17

How to denote naming amine prefix’s

Answer 17

-if 2x identical groups present (prefix=di)
-if3x identical groups present (prefix=tri)
e.g. dipropanamine

Question 18

How to name an amine with 2x different alkyl groups present

Answer 18

alphabetically listed
e.g. ethylmethanamine, ethyldiproanamine

Question 19

How to name an amine if other functional groups are present in molecule

Answer 19

presence of amine groups denoted using amino
e.g. 2-aminoethanoic acid

Question 20

Memorise the nomenclature list and write down (order of highest–>lowest priority)

Answer 20

Carboxylic acid (suff-oic acid) (pre-carboxy)
Ester (oate) (alkoxy carbonyl)
Amide (amide) (amido)
Aldehyde (al) (formyl)
ketone (one) (oxo)
Alcohol (ol) (hydroxy)
Amine (amine) (amino)
Alkane (ane) (alkenyl)
Alkene (ene) (alkyl)
Akylhalide only pre-halo

Question 21

Describe the boiling point of alcohols, carboxylic acid, amine and amide

Answer 21

All able to form hydrogen bonds
-NOF attached to hydrogen and lone pairs of self
-strong h bond gives all groups a higher bp than an alkane of similar mass
-increase length of carbon chains increase bp
-due to increase size of molecule allowing for stronger dispersion forces
-more energy required to overcome forces

Question 22

What occurs to the bp of primary, secondary and tertiary alcohols

Answer 22

decreases from prim–>tertiary
- carbon chain restricting H bond formation with other molecules

Question 23

Describe the solubility of alcohols, carboxylic acid, amine and amide

Answer 23

In water
Small groups able to dissolve in water due to ability to form H bonds with water molecules
- increase chain length= decrease solubility
-disrupts formation of H bonds
-molecule becomes more non-polar

In organic solvents
non-polar therefore increase carbon chain length will increase solubility (as long chain=non-polar)
more dispersion forces can be formed w/long chain however, will not be as strong as H bonds

Question 24

Describe the boiling point of aldehydes, ketones and esters

Answer 24

Only able to form dipole-dipole forces
-have no NOF on self hydrogen bonds
-increase BP than alkanes as dipole-dipole forces are stronger than dispersion
-increase chain length will increase bp as large molecule, with large molecular mass, allows for increase in dispersion forces

Question 25

Describe the solubility of ketones, aldehydes and esters

Answer 25

In water Although no H bonds with own molecule, small chains can form H bonds with water=soluble - increasing length will decrease solubility in water due to increased non-polarity of molecule In organic solvent non-polar therefore increase carbon chain length will increase solubility (as long chain=non-polar) more dispersion forces can be formed w/long chain however, will not be as strong as H bonds