Hydrocarbons: Integrated Visual Reference

Hydrocarbon Classification

Cₙ$H_{2}$ₙ₊_{2} (Alkane, $sp^{3}$)  →  Cₙ$H_{2}$ₙ (Alkene, $sp^{2}$)  →  Cₙ$H_{2}$ₙ₋_{2} (Alkyne, sp)
    CC                       CC=C                      CC#CC
(Ethane)                  (Propene)                (But-2-yne)

Alkane Conformation Energy Diagram (Butane)

Energy (kJ/mol above anti)
~19 |   *FE*
~16 |           *E*
~3.8|      *G*           *G*
0   |*A*                         *A*
    0°   60°  120°  180°  240°  300°  360°
    (Dihedral Angle)

FE=Fully Eclipsed, E=Eclipsed, G=Gauche, A=Anti

Addition Reactions of Propene — Decision Tree

Propene (CC=C)
│
├── + HBr, no peroxide → [ionic, Markovnikov] → 2-bromopropane (CC(Br)C)
│
├── + HBr, ROOR → [radical, anti-Markovnikov] → 1-bromopropane (CCCBr)
│
├── + $H_{2}$O, $H_{2}$$SO_{4}$ → [ionic, Markovnikov] → propan-2-ol
│
├── + $Br_{2}$/$CCl_{4}$ → [anti-addition] → 1,2-dibromopropane
│
└── + $O_{3}$ then Zn/$H_{2}$O → [ozonolysis] → $CH_{3}CHO$ + HCHO

Alkyne Reduction Products

Reagent	But-2-yne (`CC#CC`) →	Product SMILES
$H_{2}$ /Lindlar's	cis-but-2-ene	`C/C=C\C`
Na/liq. $NH_{3}$	trans-but-2-ene	`C/C=C/C`
$H_{2}$ /Pd–C (excess)	butane	`CCCC`

Acidity Comparison Table

Compound	SMILES	Hybridization	% s-character	pKa	Acidity Rank
Ethyne	`C#C`	sp	50%	~25	Most acidic (1st)
Ethene	`C=C`	$sp^{2}$	33.3%	~44	Intermediate (2nd)
Ethane	`CC`	$sp^{3}$	25%	~50	Least acidic (3rd)

Anti-Markovnikov HX Selectivity

HX	+ Peroxide Works?	Reason
HBr	YES	All radical chain steps exothermic
HCl	NO	Cl• + alkene step is endothermic
HI	NO	I• causes premature chain termination
HF	NO	F• too reactive; HF also too acidic