Content:

Alkane:

Structure and physical properties (boiling point and solubility), Nomenclature (naming) Preparation (hydrogenation of alkenes, hydrolysis of Grignard reagents) Alkane reactions (halogenation/free radical substitution, combustion) Sources and uses

Bpt vs C-chain length

As Chain length^, # e-^, therefore LDF's^, so bpt^

Source: http://www.chemistryrules.me.uk/junior/organic.htm

Very good for introductory organic Chem!

As branching ↑, Surface area ↓, hence VdW’s ↓, bpt ↓

^^ Reference http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Properties-of-Alkanes-917.html

Nomenclature for alkanes

• • • • • • Find the longest carbon sequence (either a chain or within a ring). That forms the ROOT / PARENT / PRIMARY name.

Name ‘branches’ as prefixes in alphabetical order (note: do not use di, tri, tetra etc in the alphabetical ordering) Use numbering so numbers are as low as possible.

Ring structure have the prefix ‘cyclo’ rest of name.

Letters are separated from numbers using a hyphen Numbers are separated from each other using a comma

• ‘special groups’ (commonly occur, so given their own name and they remain in widespread use) https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/nomen1.htm

Very good page for nomenclature

Hydrocarbon preparation

• Hydrogenation of alkenes. H C C H +

H H

metal catalyst: Pt or Rh or Ni H H • Hydrolysis of Grignard reagents. Grignard reagent (organo magnesium) H Bt  + + Mg in dry ether BrMg  +

H

O H

H H

H

H

H H ( + MgOHBr) Note: This example shows a trivial example You would NEVER do this to get a simple, readily available alkene You would only do it to make a rare or complicated alkane.

New bond • Or by other Grignard reactions:  + OTs + BrMg  Grignard (organo magnesium)

Alkane reactions

(Functionalisation of alkanes)

http://driesnuyts.blogspot.com/2012/04/alkanes-and-radicals-introduction.html

Combustion of alkanes

• Fuels (e.g. the RM1.92 RM2.10 Ron95) are made up mostly of alkanes.

In excess oxygen • C n H 2n+2 + (1.5n+½)O 2  nCO 2 + (n+1)H 2 O • The process is exothermic and causes a large increase in volume and entropy.

Application: Sources and uses • • Uses: as fuels (e.g. Kerosine), solvents (e.g. hexane), chemical feedstock Source: Primarily from the Crude oil which is a complicated mixture of many compounds. Some long hydrocarbons are broken up to produce smaller, often more useful hydrocarbons.

Conformations

• Alkane chains and rings are in a constant state of motion/vibrations (due to background thermal energy). Alkane vhains can rotate about the C-C and rings can flex. Each ‘snapshot’ of the orientation of the molecule has it’s own energy.

Alkane ‘chain’ conformers

1 cal = 4.18 Joules http://chemistry.umeche.maine.edu/CHY251/Butane.html

Alkane ring conformers

Energy profile of cyclohexane conformers… http://www.stolaf.edu/depts/chemistry/courses/toolkits/247/js/cyclohex/

Nomenclature practice:

H C H C H H

Ethene

H H C C H H C C H H H

trans-But-2-ene

Alkenes

H H C H C H C H H

Propene

H C H H C H C C H H H H

Butene?

But-1-ene 3-Methyl-cyclohexene

Bpt of alkenes v.similar to alkanes. Why?

Similar # e- (2 less than alkane)

Dehydration of alcohols

Use a dehydrating agent e.g. c.H

2 SO 4 or Al 2 O 3 or c.H

3 PO 4 and heat. Different temps used can give different products!!! http://www.transtutors.com/chemistry-homework-help/alcohols/dehydration-of-alcohols.aspx

Dehydration of alcohols

Mechanism (how reaction happens)

http://www.education.com/study-help/article/nomenclature-structure/

Prep of alkenes Dehydrohalogenation

http://www.personal.psu.edu/users/t/h/the1/e2.htm

Dehydration of alcohols

Zaitsev's (Saytzeff) rule: For Dehydration and dehydrohalogenation, the more substituted alkene product is major product

http://www.mhhe.com/physsci/chemistry/carey/student/olc/graphics/carey04oc/ref/ch05eliminationreactions.html

Markovnikov Rule:

Cation (usually H + ) adds into the compound to make the most substituted carbocation.

Familiarity with carbocation stability is crucial in organic chemistry

https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/addene1.htm

Addition

reactions

of alkenes (X-Y)

http://www.chemguide.co.uk/mechanisms/eladd/whatis.html#top

http://www.chemguide.co.uk/mechanisms/eladd/whatis.html#top

Overall:

Can also occur via free radical mechanism

http://mhschemf6.blogspot.com/2011/05/alkene.html

Markovnikov Rule:

Cation (usually H + ) adds into the compound to make the most substituted carbocation.

Addition

reactions

of alkenes (X-X)

http://www.masterorganicchemistry.com/reaction-guide/bromination-of-alkenes-with-br2-to-give-dibromides/

Aleken + AQ Br

2 • Gives a halohydrin (+ monobormo product) http://en.wikibooks.org/wiki/Organic_Chemistry/Introduction_to_reactions/Halohydrins

Alkenes with conc. H

2

SO

4 • See the similarity with the other conc. acids https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/addene1.htm

C=C with KMnO

4

(Baeyer test)

COL/RT condition: Purple colour of permanganate solution decolourises on addition to colourless alkene. Brown solids (MnO 2 ) procuded in neutral or alkaline conditions. Very pale pink (will look almost colourless, in acidic solution)

C=C with KMnO

4

(Baeyer test)

HOT CONCENTRATED and ACIDIFIED KMnO 4

http://www.chemguide.co.uk/organicprops/alkenes/kmno4.html

Ozonolysis (cleavage using ozone, O 3 ) http://en.wikipedia.org/wiki/Ozonolysis

Ozonolysis (cleavage using ozone, O 3 ) Overall: http://en.wikipedia.org/wiki/Ozonolysis

As with all info on these slides, you should try and condense it into simple reaction equations (as above) to help begin the process of ‘connecting’ reactions. The overall equation is just to summarise the reaction and remind you.

Alkene (partial summary of) reactions.

http://skc13chem.blogspot.com/2010/08/reactions-of-alkenes-and-alcohols.html

C=C - Applications and use

• • Polymers (addition polymers – poly(styrene), PVC, poly(propene) Raw materisals for making R-X, R-OH and carbonyls

2.3 Aromatic compounds

• Answers to practice (L to R, top to bottom) Butane 2-Methylbutane 3,3-Diethyl-4-methylhexane Propylcyclopentane (3-Methyl-2-cyclopentylheptane 3,4-Diisopropyl-2,5,6-trimethylheptane

http://en.wikibooks.org/wiki/A-level_Chemistry/OCR_%28Salters%29/Reactions_of_arenes

3.0 Aliphatic alcohols

R

Nucleophilic substitution in alcohols

H H (1) H

..

Nu ( ) C  +

:

O  R C (2) H H (1) New bond forms between C and Nu (sharing Nu's e- pair) (2) Old bond breaks between C and O Nu + _ :OH