Carbon and its Various Shapes and Functions

Question 1

What shape is a car anion?

Answer 1

Tetrahedral

Question 2

What shape is a carbocation?

Answer 2

Trigonal planar

Question 3

What is the general formula of Alkanes?

Answer 3

CnH2n+2

Question 4

What are the different types of name?

Answer 4

Systematic
Semi-systematic (part systematic, part trivial)
Common/trivial

Question 5

Give the rules for nomenclature.

Answer 5

1. Identify largest chain of C atoms (other bits are substituents)
2. Number the chain (substituents have the lowest numbers)
3. List substituents in alphabetical order (ignore di-, tri-, ect.)
4. Hyphens between numbers and letters, commas between numbers

Question 6

What is the general formula of cycloalkanes?

Answer 6

CnH2n

Question 7

Cycloalkanes occur in many important compounds like…

Answer 7

Steroids

Question 8

What are stereoisomers?

Answer 8

Same formulae and bond pattern but a different arrangements of the atom in space.

Question 9

What is a chiral compound?

Answer 9

A compound containing a carbon atom that has four different groups attached. Eg Lactic Acid. C attached to H, CH3, OH and COOH

Question 10

What is a geometric isomer?

Answer 10

An isomer with the opposite arrangement (cigs or trans) to the other one.

Question 11

What is an enantiomer?

Answer 11

An asymmetrical non-superimposable mirror image

Question 12

How do enantiomers differ from each other?

Answer 12

They are mirror images and have opposite effects on plane polarised light.

Question 13

What is special about plane polarised light?

Answer 13

It oscillates in one direction only.

Question 14

What effect will achiral and chiral compounds have on plane polarised light?

Answer 14

If ppl is passed through an achiral compound then it will pass through and exit without being affected.
If it is passed through a solution containing even one single enantiomer of a chiral compound then it will be rotated and is described as being optically active.

Question 15

What do you call a mixture containing equal amounts of each enantiomer?

Answer 15

Racemic mixture

Question 16

Optical isomers have identical chemical properties except…

Answer 16

When reactions occur in a chiral environment

Question 17

Will both enantiomers fit the active site of an enzyme?

Answer 17

No, only one.

Question 18

How does the E-Z convention work?

Answer 18

1. Assign priority to atom with highest mass at each end of double bond.
2. If highest priority atom is on same side call it Z
3. If highest priority atom on different side call it E

Question 19

Nucleophiles are usually…

Answer 19

Negative or partially negative

Question 20

Electrophiles are usually…

Answer 20

Positive or partially positive

Question 21

Are Alkanes nucleophiles or electrophiles?

Answer 21

Nucleophiles

Question 22

What are the main reactions that Alkanes undergo?

Answer 22

Addition Eg
Bromination (Br2) (dipole induced by electron rich double bond)
Hydrobromination (HBr)
Hydration (H2O) (H+ produced with alcohol)
Hydrogenation (H2) (Hs delivered to same side of Alkene (cis))
Dihydroxylation (kMnO4, NaOH) (produces diols (glycols))
Oxidation with Acidic Permangenate (KMnO4, H3O+)
Ozonolysis (O3)

Question 23

Addition to unsymmetrical Alkanes can form more than one product but one is favoured over the others, why?

Answer 23

Markovnikov’s rule - the H from an HX bond will attach to the Carbon atom that already has the most Hs attached.

Question 24

Describe the stability of carbocations (tertiary, secondary, etc.)

Answer 24

Tertiary > secondary > primary > methyl
This is because the alkyl groups stabilise the carbocation (electron donating effect)
The most stable carbocation available will form (markovnikovs rule)

Question 25

What happens during ozonolysis?

Answer 25

Lysis or cleavage using ozone Two stage process - overall reaction Ozone is an electrophile Products of ozonolysis - Break C -C double bond and add O to each end.

Question 26

How many addition reactions does acetylene undergo?

Answer 26

Two successive addition reactions. Markovnikovs rule is obeyed

Question 27

How would acetylene undergo hydrobromination?

Answer 27

The H-Br bond breaks, with the electrons from the triple bond stealing the H. The Br then nucleophilically attacks the carbocation. More HBr is used to add a rod the double bond.

Question 28

What is produced in hydrogenation of but - 2 - yne?

Answer 28

With Pd catalyst - butane | With Lindlar's catalyst - cis-but-2-ene (useful for making cis double bonds)

Question 29

What is Hydration of Acetylene good for?

Answer 29

Useful for making ketones

Question 30

What happens in a substitution reaction?

Answer 30

One substituents is removed and replaced by another

Question 31

What happens in an elimination reaction?

Answer 31

A substituents is removed

Question 32

What makes a good nucleophiles?

Answer 32

Negative ions better than corresponding neutral atoms Elements lower in group better than elements higher in same group More electronegative elements in same row are poorer nucleophiles

Question 33

What affects the rate of nucleophilic substitution with hydroxide?

Answer 33

``` Steric hinderance As steric hinderance increases, relative rate decreases. Methyl - 20 Primary - 1 Secondary - 0.3 ``` Tertiary is an exception - 10^6 (this suggests different mechanism)

Question 34

Sn2 mechanism has how many steps and how many molecules in RDS?

Answer 34

Two molecules in RDS and is a one step process (concerted reaction)

Question 35

Sn1 mechanism has how many steps and how many molecules in RDS?

Answer 35

One step and two molecules in RDS

Question 36

What kind of reactions to tertiary alkyl halides undergo and why?

Answer 36

Sn1 because: 1. Steric effects - nucleophilic attack hindered by many alkyl groups. 2. Electronic effects - tertiary carbocation is stable (electron donating effect)

Question 37

What is the problem with elimination and substitution reactions?

Answer 37

They may compete with each other.

Question 38

Who won the Nobel prize for the Grignard reagent and when?

Answer 38

Victor Grignard - 1912

Question 39

What did Victor Girgnard do?

Answer 39

He reacted Mg with Alkyl Halides (CH3-I) which turned the carbon into a nucleophile. It becomes a strong base so will react violently with water meaning anhydrous conditions are needed.

Question 40

What are the reactions of alcohols?

Answer 40

1. Reactions of O-H bond (not good for making CH3O-) 2. Reactions of lone pairs 3. Reactions of C-O bond (acid conditions needed) 4. Reactions of alpha C- H bond (oxidation with Cr 6+)

Question 41

pKa values

Answer 41

``` Higher values - less acidic HCl - -7 Acetic Acid - 5 Water - 14 Methanol - 16 ```

Question 42

Why do ethers have high bps?

Answer 42

H bonding

Question 43

Why is diethyl ether a good solvent?

Answer 43

It has a low bp