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Questions and Answers
What is the general formula for alkanes?
What is the general formula for alkanes?
Which alkane has the molecular formula C5H12?
Which alkane has the molecular formula C5H12?
What happens to the boiling point of liquid alkanes as the molecular weight increases?
What happens to the boiling point of liquid alkanes as the molecular weight increases?
How do the physical properties of cycloalkanes compare to those of alkanes with open chains?
How do the physical properties of cycloalkanes compare to those of alkanes with open chains?
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How does chain branching affect the boiling point of branched alkanes?
How does chain branching affect the boiling point of branched alkanes?
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What is the ideal bond angle for cycloalkanes?
What is the ideal bond angle for cycloalkanes?
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Which cycloalkane is the most reactive due to angle strain?
Which cycloalkane is the most reactive due to angle strain?
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How does the reactivity of cyclopropane compare to that of alkanes?
How does the reactivity of cyclopropane compare to that of alkanes?
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What is the primary characteristic of alkenes?
What is the primary characteristic of alkenes?
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When naming alkenes, what must be indicated if there are four or more carbon atoms in the chain?
When naming alkenes, what must be indicated if there are four or more carbon atoms in the chain?
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Study Notes
Pharmaceutical Organic Chemistry I (PMC 102)
- Course taught by Dr. Asmaa Yassen at GALALA UNIVERSITY, powered by Arizona State University.
- Course website: gu.edu.eg
Classification of Carbon Atoms
- Primary (1°): A carbon atom bonded to one other carbon atom.
- Secondary (2°): A carbon atom bonded to two other carbon atoms.
- Tertiary (3°): A carbon atom bonded to three other carbon atoms.
- Quaternary (4°): A carbon atom bonded to four other carbon atoms.
Alkanes
- Saturated hydrocarbons, containing only single bonds.
- General formula: CnH2n+2.
- Nomenclature follows specific rules.
- Root word + ane
- Examples: methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), pentane (C5H12), etc
Alkane: Physical Properties
- C1-C5 are gases at room temperature.
- C6-C10 are liquids.
- Above C11 are semisolids or waxy matters.
- Insoluble in water, but soluble in nonpolar solvents.
- Boiling point increases with increasing molecular weight.
- Boiling point decreases with branching.
Alkane: Nomenclature
- For substituted alkanes, identify the longest continuous carbon chain.
- Number the chain from the end nearest the substituent.
- Name and locate each substituent group.
- List substituent groups alphabetically, using prefixes (di, tri, etc.) for multiple occurrences of the same group.
Alkyl Groups
- Alkyl groups are derived from alkanes by removing one hydrogen atom.
- CH3 - Methyl
- CH3CH2 - Ethyl
- Isopropyl, sec-butyl, tert-butyl
Halogenation of Alkanes
- Free radical substitution reaction (requires light or heat).
- Stability of carbon radicals follows the order: tertiary > secondary > primary.
Cycloalkanes
- A class of hydrocarbons with carbon atoms forming a ring structure.
- General formula: CnH2n
- More reactive than open-chain alkanes due to ring strain.
- Nomenclature includes the prefix "cyclo."
Nomenclature of substituted cycloalkanes
- Number the ring atoms to give substituents the lowest possible numbers.
- List substituents alphabetically.
Preparation of cycloalkanes
- A dihalogen compound is dehalogenated using Zn and Nal catalyst.
Reduction of Aromatic compounds
- Treatment of benzene and its derivatives with hydrogen gas (H2) in the presence of a catalyst(Ni) at 150-200°C forms cyclohexane
Angle Strain
- Deviation from the ideal bond angle (109.5°) in cycloalkanes leads to increased strain and reactivity.
- Cyclopropane has significant strain, while cyclopentane and cyclohexane have less (or no) strain.
Alkenes:
- Unsaturated hydrocarbons.
- Contain one or more carbon-to-carbon double bonds (C=C).
- General formula: CnH2n
- Nomenclature rules include adding "-ene" to the root name, and numbering the double bond to the lowest possible numbers.
- Classification of alkenes is based on the degree of substitution on the carbon atoms bonded to the double bond (mono-, di-, tri-, or tetrasubstituted).
Alkynes:
- Unsaturated hydrocarbons containing one or more carbon-to-carbon triple bonds (C≡C).
- General formula: CnH2n-2.
- Nomenclature rules include adding "-yne" to the root name and numbering the triple bond to the lowest possible number.
- Terminal alkynes have a hydrogen atom on one of the triple bonded carbons. Internal alkynes have carbon atoms bound to each carbon of the triple bond.
Properties of Alkynes
- Physical properties similar to corresponding alkanes and alkenes.
- Up to four carbons are gases at room temp.
- Relatively nonpolar. Dissolve in nonpolar solvents and low polarity solvents.
- Terminal alkynes are weakly acidic.
Reactions of alkynes
- Addition reactions are possible with one or two molar equivalents of a reagent.
- Hydrogenation (adding H2) can result in an alkene or an alkane.
- Partial reduction with Lindlar catalyst results in cis-alkenes.
- Reduction to trans-alkenes using Na or Li in liquid NH3.
- Addition of halogens (Br2, Cl2) results in di-, tetra-halogenated products.
- Addition of hydrogen halides (HCl, HBr) follows Markovnikov's rule.
- Anti-Markovnikov addition possible with peroxides in presence of HBr.
- Addition of water using HgSO4 in presence of H2SO4 forms ketones.
- Ozonolysis (treating with ozone and a reducing agent) cleaves the triple bond resulting in carboxylic acids.
Isomers of Alkenes
- Geometric isomers (cis-trans) exist when the two carbons bonded to the double bond have different groups attached.
- Numbering of substituents is important for determining the E/Z configuration.
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