Organic Chemistry - How To Draw Lewis Structures

The Organic Chemistry Tutor
8 Apr 201811:55
EducationalLearning
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TLDRThis educational video script offers a comprehensive guide to drawing Lewis structures for organic chemistry, focusing on the bonding preferences of common elements. It explains the typical bonding patterns for hydrogen, carbon, nitrogen, oxygen, and halogens, and provides step-by-step examples for molecules like methane, methanol, ethylamine, ethyl chloride, dimethyl ether, acetaldehyde, ethene, acetylene, and hydrazine. The script also addresses how to adjust Lewis structures for charged molecules, emphasizing the importance of electron distribution and element valency.

Takeaways
  • 🔬 Hydrogen can only form one bond, which is a fundamental rule in drawing Lewis structures.
  • 🌐 Elements like boron, carbon, nitrogen, oxygen, and fluorine can form multiple bonds, with boron typically forming three bonds in its neutral state.
  • 🔀 Carbon prefers to form four bonds, nitrogen usually forms three, and oxygen typically forms two bonds in organic chemistry.
  • 🌊 Halogens like fluorine, chlorine, bromine, and iodine generally form one bond and have seven valence electrons, needing one more to complete their octet.
  • 🌟 Sulfur often forms two bonds but can also form six, depending on its need to achieve an octet.
  • 💧 Phosphorus and nitrogen both tend to form three bonds, while silicon and carbon both form four bonds.
  • 🏙️ The Lewis structure for methane (CH4) involves carbon forming four single bonds with hydrogen atoms.
  • 🍺 Methanol (CH3OH) has a carbon bonded to three hydrogens and an oxygen, which forms two bonds and has two lone pairs.
  • 🌳 The Lewis structure for ethanamine (CH3CH2NH2) shows nitrogen forming three bonds and having one lone pair, while carbon forms four bonds.
  • 💦 Ethyl chloride (C2H5Cl) involves a carbon bonded to a chlorine atom, which forms one bond and has three lone pairs.
  • 🌈 Dimethyl ether has an oxygen in the middle forming two bonds with two methyl groups, each carbon in the methyl groups forms three bonds with hydrogens.
Q & A

  • What is the primary topic of the video?

    -The video is about how to draw basic Lewis structures within the realm of organic chemistry.

  • How many bonds can hydrogen form according to the video?

    -Hydrogen can only form one bond.

  • What is the typical number of bonds that carbon forms in its neutral state?

    -In its neutral state, carbon likes to form four bonds.

  • How does the number of bonds formed by boron differ when it has a charge?

    -When boron has a charge, it can deviate from its typical number of three bonds formed in its neutral state.

  • What is the Lewis structure for methane?

    -The Lewis structure for methane consists of a carbon atom bonded to four hydrogen atoms, each with a single bond.

  • How is the Lewis structure for methanol different from methane?

    -Methanol's Lewis structure includes a carbon atom bonded to three hydrogen atoms and one oxygen atom, which in turn is bonded to one hydrogen atom and has two lone pairs.

  • What is the general rule for elements that form three bonds?

    -Elements that form three bonds, like nitrogen, typically have one lone pair.

  • Why can't the Lewis structure for CH3CHO be drawn with a single bond between the carbon and oxygen?

    -A single bond would not satisfy the carbon's need for four bonds and the hydrogen's need for one bond, hence a double bond is required.

  • What is the functional group in C2H4 and what is its name?

    -The functional group in C2H4 is a double bond between two carbon atoms, and it is known as an alkene.

  • How does the Lewis structure for ethyl chloride differ from that of ethene?

    -In ethyl chloride, the chlorine atom forms a single bond with the carbon and has three lone pairs, whereas in ethene, there is a double bond between two carbon atoms.

  • How does the Lewis structure change for an oxygen atom when it gains or loses a hydrogen atom?

    -When oxygen gains a hydrogen atom, it loses a lone pair and acquires a positive charge. When it loses a hydrogen atom, it gains a lone pair and acquires a negative charge.

Outlines
00:00
🧪 Basic Lewis Structures in Organic Chemistry

This paragraph introduces the fundamentals of drawing Lewis structures for organic chemistry, emphasizing the bonding preferences of common elements like hydrogen, carbon, nitrogen, oxygen, and halogens. Hydrogen forms one bond, while carbon and silicon aim for four, nitrogen and phosphorus for three, and oxygen for two. Halogens typically form one bond, needing one more electron to complete their octet. The paragraph illustrates the Lewis structures of methane and methanol, highlighting the step-by-step process of determining the correct arrangement of atoms and bonds.

05:02
📚 Drawing Lewis Structures for Various Organic Molecules

The second paragraph delves into the Lewis structures of more complex organic molecules, including ethylamine (CH3CH2NH2), ethyl chloride (CH3CH2Cl), and dimethyl ether. It explains the process of drawing Lewis structures by starting with the most electronegative atoms and ensuring that all atoms achieve their preferred number of valence electrons. The paragraph also covers the Lewis structures of acetaldehyde (CH3CHO), ethene (C2H4), and acetylene (C2H2), introducing the concepts of alkenes and alkynes with double and triple bonds, respectively. Additionally, it discusses the Lewis structure of hydrazine, a molecule with nitrogen atoms forming both single and triple bonds.

10:03
🔋 Impact of Charges on Lewis Structures

The final paragraph addresses the impact of charges on the Lewis structures of molecules, specifically focusing on methanol and its anions and cations. It explains how the removal of a hydrogen atom from methanol results in a negatively charged oxygen with three lone pairs, while the addition of a hydrogen ion to methanol leads to a positively charged oxygen with one lone pair. The paragraph reinforces the idea that oxygen's bonding and lone pair count can vary depending on its charge state, providing a clear example of how to adjust Lewis structures to reflect ionic changes.

Mindmap
Keywords
💡Lewis Structures
Lewis Structures are graphical representations of molecules that show the arrangement of atoms and the valence electrons around them. They are fundamental to understanding organic chemistry as they help visualize how atoms bond together. In the video, Lewis Structures are used to illustrate the bonding patterns in various molecules, such as methane and methanol, emphasizing their importance in depicting the connectivity and electronic arrangements in organic compounds.
💡Hydrogen
Hydrogen is an element with one valence electron, which means it can form only one bond to achieve a stable electron configuration. In the context of the video, hydrogen's bonding capacity is highlighted as it can only form one bond, as seen in the Lewis Structures of methane (CH4) and methanol (CH3OH), where each hydrogen atom is bonded to a carbon or oxygen atom.
💡Carbon
Carbon is a key element in organic chemistry, known for its ability to form four bonds due to its four valence electrons. The video explains that carbon typically forms four bonds in its neutral state, as demonstrated in the Lewis Structures of methane and ethylene (C2H4), where carbon atoms are bonded to four other atoms to satisfy the octet rule.
💡Oxygen
Oxygen is another important element in organic chemistry, with six valence electrons, allowing it to form two bonds and have two lone pairs in its neutral state. The video script discusses how oxygen forms two bonds in methanol and how its bonding and lone pair configuration changes when it gains or loses a hydrogen atom, resulting in a negative or positive charge.
💡Nitrogen
Nitrogen, with five valence electrons, tends to form three bonds to complete its octet. The video mentions nitrogen's bonding preference, as seen in the Lewis Structure of ethylamine (CH3CH2NH2), where the nitrogen atom forms three bonds and has one lone pair.
💡Halogens
Halogens, such as fluorine, chlorine, bromine, and iodine, are elements that typically form one bond and have three lone pairs due to their seven valence electrons. The video script uses halogens as an example of elements that seek to gain one electron to achieve a stable octet, as seen in the Lewis Structure of ethyl chloride (CH3CH2Cl), where chlorine forms a single bond.
💡Sulfur
Sulfur, with six valence electrons, can form two or six bonds depending on the situation. The video explains that sulfur can either gain two electrons to complete its octet or give away all six to form six bonds, as in the case of sulfate ions.
💡Phosphorus
Phosphorus is similar to nitrogen in that it has five valence electrons and typically forms three bonds. The video script briefly mentions phosphorus's bonding preference, which is consistent with its need to achieve an octet.
💡Silicon
Silicon, like carbon, has four valence electrons and tends to form four bonds. The video script notes that silicon's bonding behavior is analogous to that of carbon, as it also seeks to form four bonds to satisfy the octet rule.
💡Aldehyde
An aldehyde is a functional group characterized by a carbon atom double-bonded to an oxygen atom (C=O), often with a hydrogen atom or an alkyl group attached to the carbon. The video script introduces acetaldehyde (CH3CHO) as an example of an aldehyde, highlighting the importance of the C=O double bond in its Lewis Structure.
💡Charges
Charges in the context of the video refer to the positive or negative electrical properties of atoms or ions. The video script discusses how the presence of charges affects the Lewis Structures of molecules, particularly oxygen, which can have different numbers of lone pairs and bonds depending on whether it has a positive or negative charge.
Highlights

Introduction to drawing basic Lewis structures in organic chemistry.

Hydrogen can only form one bond.

Boron forms three bonds in its neutral state and can deviate when charged.

Carbon forms four bonds in its neutral state.

Nitrogen forms three bonds, oxygen two, and halogens one.

Halogens have seven valence electrons and need one more to complete their octet.

Sulfur can form two or six bonds depending on its valence electron configuration.

Phosphorus forms three bonds, and silicon forms four bonds like carbon.

Lewis structure of methane (CH4) is explained with carbon forming four bonds with hydrogen.

Lewis structure of methanol (CH3OH) is detailed, showing carbon, hydrogen, and oxygen bonding.

General trends for elements forming three bonds typically include one lone pair.

Oxygen forms two bonds and has two lone pairs when neutral.

Halogens form one bond and have three lone pairs.

Elements like carbon, nitrogen, oxygen, and fluorine aim for an octet of electrons.

Hydrogen, being in the first row, can only hold a maximum of two electrons.

Lewis structure of ethylamine (CH3CH2NH2) is explained with nitrogen forming three bonds.

Lewis structure of ethyl chloride (CH3CH2Cl) is detailed with chlorine forming one bond and having three lone pairs.

Lewis structure of dimethyl ether is explained with oxygen forming two bonds and having two lone pairs.

Lewis structure of acetaldehyde (CH3CHO) is detailed with a carbon-oxygen double bond.

Lewis structure of ethene (C2H4) is explained with a carbon-carbon double bond.

Lewis structure of acetylene (C2H2) is detailed with a carbon-carbon triple bond.

Lewis structure of hydrazine (N2H4) is explained with nitrogen forming three bonds and having one lone pair.

Impact of charges on Lewis structures, such as CH3O-, CH3OH, and CH3OH+, is discussed.

Oxygen's bonding changes with charge: one bond with a positive charge, three bonds with a negative charge.

Transcripts

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Related Tags
Lewis StructuresOrganic ChemistryBond FormationMethaneMethanolEthanolAldehydesAlkenesAlkynesHydrazinesIon Charges