Resonant structure of ethyl cinnamate
Ethyl cinnamate has a unique chemical structure. In the field of organic chemistry, the study of the resonance structure is crucial to understand its chemical properties and reactivity.

Principle of resonance structure
Resonant structure is based on the concept of electron delocalization. In ethyl cinnamate molecules, electrons are not fixed between specific atoms, but can move delocalized within a certain range due to the presence of a conjugated system. This delocalization of electrons allows molecules to be represented by a variety of resonance formulas. These resonance formulas do not represent different real molecules, but describe different limit states of electron distribution in molecules. The true structure of the molecule is a hybrid of all these resonant structures, which combines the characteristics of each resonant structure and is more stable than any single resonant structure.

Resonance Structure Analysis of Ethyl Cinnamate
1. ** Double Bond Migration Resonance **: In the ethyl cinnamate molecule, a conjugated system is formed between the benzene ring and the carbon-carbon double bond and the ester group. Taking the part connected to the benzene ring and the double bond as an example, the π electrons on the double bond can migrate to the benzene ring to form a new resonance structure. During this resonance process, the electron cloud distribution of the benzene ring changes, and the electron part originally on the double bond is transferred to the benzene ring, which increases the electron cloud density at some positions of the benzene ring, and decreases the electron cloud density of the double bond accordingly.
2. ** Ester group participates in resonance **: The carbonyl group (C = O) in the ester group also participates in resonance. The π electron of the carbonyl group can be conjugated with the adjacent carbon-carbon double bond, and the electron can be delocalized on the carbonyl oxygen atom, the carbonyl carbon atom and the carbon-carbon double bond connected to it. At this time, the carbonyl oxygen atom will have a partial negative charge, while the carbon atom connected to it has a partial positive charge. This change in charge distribution affects the chemical activity of the ethyl cinnamate molecule. For example, in nucleophilic reactions, the partially positively charged carbonyl carbon atom is more susceptible to attack by the nucleophilic test agent.
3. ** Conjugated System Extended Resonance **: The conjugated system of the entire ethyl cinnamate molecule can be regarded as a continuous electron delocalization region. Starting from the benzene ring, through the carbon-carbon double bond, and extending to the ester group, the electrons can be delocalized within this large conjugation range. This broad conjugation effect makes the molecule highly stable, and it is also reflected in spectral properties. For example, characteristic absorption peaks appear in the ultraviolet-visible spectrum, which are related to the energy required for electron transitions in the conjugated system.

Through in-depth analysis of the resonance structure of ethyl cinnamate, we can better understand its reaction behavior and application potential in organic synthesis, medicinal chemistry and other fields.