Wk 5: Organic Compounds

Question 1

Why is carbon the central biological element?

Answer 1

• Valency of 4
• Ability to form long chains (framework for structure and stability)
• Oxide must not be too much more stable than pure element
• Bond to H must be quite strong, compared to H-O

Question 2

What are hydrocarbons

Answer 2

• H and C molecules
• non-polar (insoluble in H2O)

Question 3

What are aliphatic and aromatic compounds

Answer 3

• Aliphatic
  
  • Carbon atoms form non-cyclic chains, branched chains and non-aromatic rings
• Aromatic
  
  • unsaturated
  • one or more planar rings
    
    • 3 conjugated double bonds
    • delocalised pi-electrons

Question 4

What is a functional group?

Answer 4

• Specialised groups of atoms in a specific bonding arrangement, attached to a simple framework
• Responsible for characteristic chemical reactions of molecules
• Enhance physical and chemical properties of organic compounds
• Normally contain O or N

Question 5

What are families of organic compounds?

Answer 5

• clustered on basis of structural functional groups
• have the same functional group, but different carbon frameworks

Question 6

Saturated vs unsaturated

Answer 6

Saturated: Composed entirely of single bonds and saturated with hydrogen

Unsaturated: 1+ double/triple bonds between C atoms

Question 7

Alkanes

Answer 7

• Saturated
• Functional group
  
  • C-C and C-H (single bonds)
• General formula
  
  • CnH2n+2

Question 8

What is an alkyl group?

Answer 8

• Alkane with one less hydrogen atom
• Used to attach to another group/atom
• “R” is used to indicate any generic alkyl group

Question 9

What are alkenes?

Answer 9

• General formula: CnH2n
• Unsaturated
• Functional group: C=C

Question 10

Biomolecule examples of alkenes

Answer 10

• Limonene, pinene, myrcene (scented plant oils)
• Geranoil (roses, used in perfumes)
• Ethene (plant hormone that triggers ripening)
• Vitamin A

Question 11

Aromatic hydrocarbons

Answer 11

• Contains a benzene ring
• Aryl group: functional group containing aromatic group
• Phenyl group: specific aryl group derived from benzene -1 H atom

Question 12

Aromatic hydrocarbons as biomolecules

Answer 12

• Flavouring and spices
• Sex hormones
• Aspirin
• Aromatic amino acids
• Adrenaline

Question 13

Effects of functional groups on properties of organic molecules

Answer 13

1. Increase in molecular interactions
   
   • More energy required to seperate molecules
   • higher MP and BP than parent hydrocarbon skeleton
2. Increased solubility in polar solvents (like water)
   
   • Increased ability to from H bonds with water
   • Higher solubility
   • O or N atoms promote H bond formation

Question 14

Properties of Alcohols

Answer 14

• Formula: ROH
• Functional group: hydroxyl (O-H)
• Naming: remove -e from parent alkane and ad -ol

Question 15

What is an isomer?

Answer 15

• Same molecular formula, different chemical structure
• Different arrangment of atoms in space
• Do not necessarily share similar chemical/physical properties

Question 16

Types of alcohols

Answer 16

Primary: 1 R group on C
Secondary: 2 R group on C
Tertiary: 3 R group on C

Question 17

Physical properties of alcohols

Answer 17

• Electronegative O in hydroxyl group = alcohols are POLAR
• Chain length increases, becomes less soluble
• Alkyl chain length increases, BP increases

Question 18

What are ethers

Answer 18

• Generic formula: ROR’
• Functional group: Alkoxy (O atom and alkyl group)
• Short chains are soluble in water, but fewer molecular interaction
  
  • Hence lower MP’s than corresponding alcohols
• Naming: alkoxyalkane
  
  • Shorter of 2 chains becomes 1st part of name with -oxy instead of -ane
  • Longer alkane chain becomes suffix for the end of the ether

Question 19

Describe aldehydes and ketones

Answer 19

• Generic Formula:
  
  • Aldehydes: RCHO
  • Ketones: RCOR’
• Carbonyl group: O and double bond
  
  • Allows polarisation and H bond formation
  • Double bond increases reactivity
• Carbonyl group attachment
  
  • Aldehyde: attached to 1 carbon atom
  • Ketone: attached to 2 C atoms (often 2 alkyl groups)
• Naming
  
  • Aldehyde: -al
  • Ketone: -one

Question 20

Aldehydes and ketones in biomolecules

Answer 20

• Glucose: aldose sugar
  
  • Carbonyl group at end of the chain
• Fructose: ketose sugar
  
  • Carbonyl group in middle of chain
• Spices and flavourings
  
  • Almond, cinnamon, mint